Radio terminal, radio station, and method therefor

ABSTRACT

A radio terminal (1) is configured to transmit data using a first communication architecture type, in response to an occurrence of a request for specific data transmission when the radio terminal (1) has already been configured by a network (3) to use a second communication architecture type. This contributes to, for example, when the radio terminal has already been configured by the network to use the second communication architecture type that involves suspension and resumption of an RRC connection, facilitating effectively performing communication according to the first communication architecture type that involves data transmission over a control plane.

TECHNICAL FIELD

The present disclosure relates to a radio communication systemsupporting a plurality of communication architecture types for datatransmission.

BACKGROUND ART

The 3rd Generation Partnership Project (3GPP) has been standardizingCellular Internet of Things (CIoT). CIoT covered by 3GPP includes LongTerm Evolution enhanced Machine to Machine (LTE eMTC) and Narrowband IoT(NB-IoT). The characteristic features of LTE eMTC and NB-IoT includeultra-low User Equipment (UE) power consumption, a large number ofdevices per cell, narrowband spectrum, and extended coverage. In LTEeMTC (Category M), UE Radio Frequency (RF) bandwidth is defined as 1.4MHz. Meanwhile, in NB-IoT, it is assumed that downlink and uplink peakrates are 200 kbps or 144 kbps, and UE RF bandwidth is about 200 kHz(effective bandwidth is 180 kHz) in both uplink and downlink for furthercost optimization, low power consumption, and coverage extension.

Non Patent Literature 1 describes several communication architecturesolutions for infrequent small data transmission in the NB-IoT. Thesesolutions include an architecture for data transmission through thecontrol plane (i.e., Solution 2) and an architecture for datatransmission through the user plane (i.e., Solution 18) involvingsuspension and resumption of an RRC connection. In Non Patent Literature1, support of the solution 2 is mandatory for both the UE and thenetwork, while support of the solution 18 is optional for both the UEand the network.

The solution 2 is based on the lightweight Core Network (CN)architecture for CIoT. In the lightweight CN architecture, inconsideration of typical use cases of CIoT devices, the core networkonly supports a limited number of functions, compared to the CN entitiesin the existing LTE (i.e., Mobility Management Entity (MME), ServingGateway (S-GW), and Packet Data Network Gateway (P-GW)). FIG. 1 shows anetwork architecture for CIoT in a non-roaming case.

CIoT Serving Gateway Node (C-SGN) is a new logical network entity. TheC-SGN is a CN node having both the control plane (CP) and the user plane(UP). The C-SGN provides a limited Mobility Management (MM) procedurefor CIoT devices, a small data transmission procedure, a securityprocedure for small data transmission, and a termination of an SGiinterface for the non-roaming case. The P-GW function may be separatedfrom the C-SGN. In this case, an S5 interface is used between the C-SGNand the P-GW. In a roaming case, the C-SGN provides an S8 interface.

The S1-lite interface is an optimized version of S1-C(S1-MME). TheS1-lite interface supports S1 Application Protocol (S1AP) messages andinformation elements (IEs) for CIoT procedures, and also supportsoptimized security procedures. For efficient small data transmission,user data is delivered through the SLAP layer.

Specifically, in the Mobile Originated (MO) small data transmission forthe non-roaming case, the UE transmits an uplink Non-Access Stratum(NAS) message carrying a small data packet (e.g., Internet Protocol(IP), non-IP, short message service (SMS)). This uplink NAS message isdelivered to the C-SGN via the CIoT Base Station (CIoT BS). This uplinkNAS message is transmitted on a Signaling Radio Bearer (SRB). Thus, asetup of a Data Radio Bearer (DRB) is not required. Further, AccessStratum (AS) Security may be omitted.

The C-SGN decrypts the uplink NAS message to obtain the small datapacket. The C-SGN forwards the small data packet according to the datatype of the small data packet. For IP small data, the C-SGN sends it onthe SGi interface. For SMS, the C-SGN sends it to an entity related toSMS (e.g., SMS Gateway Mobile Services Switching Center (SMS-GMSC), SMSInterworking Mobile Services Switching Center (SMS-IWMSC), SMS router).For Non-IP small data, the C-SGN sends it to the Service CapabilityExposure Function (SCEF).

In the Mobile Terminated (MT) small data transmission for thenon-roaming case, the C-SGN transmits a downlink NAS message carrying asmall data packet to the UE through the CIoT BS. Also for the small datapacket transmission in downlink, a DRB is not required and AS securitymay be omitted.

The CIoT BS shown in FIG. 1 is a base station in the CIoT Radio AccessNetwork (CIoT RAN). An LTE eNB configured to be connected to the C-SGNmay be used instead of the CIoT BS in FIG. 1. This LTE eNB may be an eNBthat supports LTE eMTC.

Meanwhile, the architecture according to the solution 18 providesinfrequent small data transmission on the user plane. The architectureaccording to the solution 18 has the feature of reusing informationobtained from the previous RRC connection for the subsequent RRCconnection setup, thereby reducing the signaling required for UE RadioResource Control (RRC) state transition.

Specifically, a UE enters the RRC-Idle mode from the RRC-Connected modeand retains information about the RRC connection (e.g., an AccessStratum Security Context, bearer related information (incl. RoHC stateinformation), and L2/1 parameters when applicable) while it is inRRC-Idle mode. Similarly, an eNB retains information about the RRCconnection of the UE (e.g., Access Stratum Security Context,bearer-related information (incl. RoHC state information), and L2/1parameters when applicable). Further, the eNB and MME retain S1AP UEContexts. Furthermore, the eNB retains S1-U tunnel addresses.

When returning to the RRC-Connected mode, the UE sends an RRC ConnectionResume Request to the eNB. The eNB restores a DRB(s), a securitycontext, an S1AP connection, and an S1-U tunnel(s) based on thepreviously retained information about the RRC connection. Further, theeNB informs the MME of a UE state change using a new S1AP message (e.g.,S1AP: UE Context Resume Request). The MME returns the Evolved PacketSystem (EPS) Connection Management (ECM) state of the UE to theECM-Connected state and then sends a Modify Bearer Request message tothe S-GW. As a result, the S-GW recognizes that the UE is in theconnected state and hence becomes ready to transmit downlink datatowards the UE.

In the solution 18, the UE can return to RRC-Connected and ECM-Connectedwithout transmitting a NAS message (i.e., Service Request). Further, ascompared with the legacy RRC connection setup procedure, the followingRRC messages can be removed:

-   -   RRC Connection Setup Complete;    -   RRC Security Mode Command;    -   RRC Security Mode Complete;    -   RRC Connection Reconfiguration; and    -   RRC Connection Reconfiguration Complete.

The above-described solution 2 and solution 18 are also referred to as“Data over NAS (DoNAS)” and “AS context caching”, respectively.Alternatively, the solution 2 and solution 18 are also referred to as“Control Plane CIoT EPS optimisation” and “User Plane CIoT EPSoptimisation”, respectively.

At this time, it is assumed that the solution 2 does not use AccessStratum (AS) security and PDCP, and neither the solution 2 nor thesolution 18 uses the SRB 2.

In some implementations, the solution to be applied to the UE may beselected by the core network (i.e., MME, C-SGN) in the attach procedurefor this UE. Alternatively, in some implementations, the UE itself mayselect the solution. The core network or the UE makes an initialselection of the solution to be applied to the UE, and after that thecore network or the UE changes the selected solution.

Non Patent Literature 2 describes that the UE may determine, during theattach procedure, which of the Solution 2 architecture and the Solution18 architecture it would prefer to use. Further, Non Patent Literature 2describes that an AS procedure or a NAS procedure may includeinformation for allowing the network to select the solution 2 or thesolution 18 for data transmission.

Non Patent Literature 3 describes that the UE may include a “PreferredNetwork Behaviour” indication in a NAS message such as an AttachRequest, a PDN Connection Request, and a Tracking Area Update (TAU)Request. The Preferred Network Behaviour indicates a solution that theUE can support or that the UE would prefer to use. Specifically, thePreferred Network Behaviour may include the following information:

-   -   Whether Control Plane CIoT EPS optimisation is supported;    -   Whether User Plane CIoT EPS optimisation is supported;    -   Whether Control Plane CIoT EPS optimisation is preferred or        whether User Plane CIoT EPS optimisation is preferred;    -   Whether S1-U data transfer is supported;    -   Whether SMS transfer without Combined Attach is requested; and    -   Whether Attach without PDN Connectivity is supported.

CITATION LIST Non Patent Literature

-   Non Patent Literature 1: 3GPP TR 23.720 V1.2.0 (2015-11), “3rd    Generation Partnership Project; Technical Specification Group    Services and System Aspects; Architecture enhancements for Cellular    Internet of Things (Release 13)”, November 2015-   Non Patent Literature 2: 3GPP R2-156645, Qualcomm Incorporated,    “NB-IoT SA2 architecture implications”, 3GPP TSG RAN WG2 #92,    Anaheim, USA, 16-20 Nov. 2015-   Non Patent Literature 3: 3GPP S2-160448, Alcatel-lucent, Vodafone,    Qualcomm, Nokia Networks, “Introduction of attach procedure changes    for CIoT EPS optimization”, 3GPP TSG SA WG2 Meeting #113, St. Kitts,    Jan. 25-29, 2016

SUMMARY OF INVENTION Technical Problem

The inventors have studied communication architectures for CIoT andcommunication architectures for reducing power consumption of a radioterminal (UE), and found several problems including three problemsdescribed below in detail.

Firstly, according to the teachings of the above-mentioned Non PatentLiterature 1 to 3, it is not clear what sort of event could cause the UEto perform the communication of the solution 2 (i.e., data transmissionover the control plane (NAS)) when the UE has already been configured bythe network (e.g., MME, C-SGN) to use the solution 18.

Secondly, according to the teaching of the above-mentioned Non PatentLiterature 1 to 3, it is not clear how the information (context) aboutthe RRC connection retained in the UE is handled when the UE isrequested by a higher layer to transmit data in accordance with thesolution 2 (i.e., data transmission over NAS) while suspending the RRCconnection for the solution 18 (i.e., communication involving suspensionand resumption of the RRC connection). The higher layer is, for example,a service/application layer, an IP Multimedia Subsystem (IMS) layer, ora NAS layer.

Thirdly, according to the teachings of the above-mentioned Non PatentLiterature 1 to 3, it is not clear which type of RRC message is used totransmit data in accordance with the solution 2 (i.e., data transmissionover the control plane (NAS)) when the UE is requested by the higherlayer to transmit data in accordance with the solution 2 whilesuspending the RRC connection for the solution 18. For example, assumethat an RRC connection resume message used for resuming the RRCconnection is also used for the data transmission in accordance with thesolution 2. In this case, the eNB receives this RRC connection resumemessage, but it might fail to recognize that this RRC connection resumemessage contains a NAS message carrying data.

In light of the above problems, one of the objects to be attained byembodiments disclosed herein is to provide an apparatus, a method, and aprogram that, when a radio terminal has already been configured by anetwork (e.g., MME, C-SGN) to use a communication architecture typeinvolving suspension and resumption of an RRC connection, facilitateeffectively performing communication according to another communicationarchitecture type involving data transmission on a control plane (NAS).

It should be noted that this object is only one of the objects to beattained by the embodiments disclosed herein. Other objects or problemsand novel features will become apparent from the following descriptionand accompanying drawings.

Solution to Problem

In a first aspect, a radio terminal includes a memory and at least oneprocessor coupled to the memory. The at least one processor isconfigured to support a plurality of communication architecture types.The plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection.The suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state. The resumption of the RRC connection includesreusing the retained context at the time of a setup of a subsequent RRCconnection in order for the radio terminal to transition from the RRCidle state to an RRC connected state. The at least one processor isfurther configured to, in response to an occurrence of a request forspecific data transmission when the radio terminal has already beenconfigured by a network to use the second communication architecturetype, transmit data using the first communication architecture type.

In a second aspect, a method in a radio terminal includes beingconfigured by a network with at least one of a plurality ofcommunication architecture types. The plurality of communicationarchitecture types include: (a) a first communication architecture typein which a data packet is transmitted via a control plane; and (b) asecond communication architecture type in which a data packet istransmitted via a user plane and that involves suspension and resumptionof a Radio Resource Control (RRC) connection. The suspension of the RRCconnection includes retaining in the radio terminal a context of aprevious RRC connection while the radio terminal is in an RRC idlestate. The resumption of the RRC connection includes reusing theretained context at the time of a setup of a subsequent RRC connectionin order for the radio terminal to transition from the RRC idle state toan RRC connected state. The method further includes, in response to anoccurrence of a request for specific data transmission when the radioterminal has already been configured by the network to use the secondcommunication architecture type, transmitting data using the firstcommunication architecture type.

A third example aspect is a program including instructions (softwarecodes) that, when loaded into a computer, causes the computer to performa method according to the above second example aspect.

Advantageous Effects of Invention

The above example aspects can provide an apparatus, a method, and aprogram that, when a radio terminal has already been configured by anetwork (e.g., MME, C-SGN) to use a communication architecture typeinvolving suspension and resumption of an RRC connection, facilitateeffectively performing communication according to another communicationarchitecture type involving data transmission on a control plane (NAS).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing an example of a CIoT architecture;

FIG. 2 is a view showing a configuration example of a radiocommunication network according to some embodiments;

FIG. 3 is a sequence diagram showing an example of a communicationprocedure according to a first embodiment;

FIG. 4 is a sequence diagram showing an example of a communicationprocedure according to a second embodiment;

FIG. 5 is a sequence diagram showing an example of a communicationprocedure according to a third embodiment;

FIG. 6 is a sequence diagram showing an example of a communicationprocedure according to a fourth embodiment;

FIG. 7 is a sequence diagram showing an example of a communicationprocedure according to a fifth embodiment;

FIG. 8 is a sequence diagram showing an example of a communicationprocedure according to a sixth embodiment;

FIG. 9 is a sequence diagram showing an example of a communicationprocedure according to a seventh embodiment;

FIG. 10 is a sequence diagram showing another example of thecommunication procedure according to the seventh embodiment;

FIG. 11 is a block diagram showing a configuration example of a radioterminal according to some embodiments;

FIG. 12 is a block diagram showing a configuration example of a basestation according to some embodiments; and

FIG. 13 is a block diagram showing a configuration example of a corenetwork node according to some embodiments.

DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments will be described in detail withreference to the drawings. The same or corresponding elements aredenoted by the same signs throughout the drawings, and repeateddescriptions will be omitted as necessary for the sake of clarity.

Each of the embodiments described below may be used individually, or twoor more of the embodiments may be appropriately combined with oneanother. These embodiments have novel features different from eachother. Accordingly, these embodiments contribute to attaining objects orsolving problems different from each other and to achieving advantagesdifferent from each other.

The following descriptions on the embodiments mainly focus on radiocommunication networks for CIoT terminals including LTE eMTC and NB-IoT.However, these embodiments may be applied to communication of other UEsin LTE, LTE-Advanced, and modified versions thereof. That is, theseembodiments may be applied to radio networks for communication of otherUEs related to LTE, LTE-Advanced, and modified versions thereof.Furthermore, these embodiments are not limited to LTE, LTE-Advanced, andmodified versions thereof, and may be applied to other radiocommunication networks.

First Embodiment

FIG. 2 shows a configuration example of a radio communication networkaccording to some embodiments including this embodiment. In the exampleshown in FIG. 2, a UE 1 which functions as a CIoT device communicateswith an application server 4 through a CIoT Radio Access Network (RAN) 2and a Core Network (CN) 3. The RAN 2 supports a plurality ofcommunication architecture types for data packet transmission regardingCIoT. The RAN 2 broadcasts in a cell, by using for example a MasterInformation Block (MIB) or a System Information Block (SIB), informationthat explicitly or implicitly indicates the plurality of communicationarchitecture types supported by the RAN 2. The UE 1 supports thesecommunication architecture types. The CN 3 supports these communicationarchitecture types. The CN 3 may include dedicated CNs (DCNs) eachassociated with a different one of the communication architecture types.

The UE 1 may support either one or both of LTE eMTC and NB-IoT. In otherwords, the UE 1 may support either one or both of the CIoT RAT (NB-IoTRAT) and the LTE RAT (eMTC). The RAN 2 may include either one or both ofa CIoT BS supporting the CIoT RAT (NB-IoT RAT) and an eNB supporting theLTE RAT (eMTC). The CN 3 may include a C-SGN, or an MME and an S-GW, orboth. The CN 3 may further include other network entities such as aP-GW, a Home Subscriber Server (HSS), a Service Capability ExposureFunction (SCEF), and a Policy and Charging Rules Function (PCRF).

In some implementations, the plurality of communication architecturetypes may include first and second communication architecture typescorresponding respectively to the solutions 2 and 18, which aredisclosed in Non Patent Literature 1. The first communicationarchitecture type can be referred to as “Data over NAS (DoNAS)” or“Control Plane CIoT EPS optimisation”. That is, in the firstcommunication architecture type, user data packets transmitted orreceived by the UE 1 are transferred through the control plane (e.g.,NAS messages transmitted between the UE and the MME/C-SGN). In the firstcommunication architecture type, the RAN 2 does not need to set up a DRBfor data packet transmission for the UE 1. Further, regarding the SRBused for data packet transmission, Access Stratum (AS) security (i.e.,ciphering and deciphering of control plane data and integrity protectionand integrity verification of control plane data) by the RAN 2 may beomitted. In other words, the processing of a Packet Data ConvergenceProtocol (PDCP) layer for the SRB used for data packet transmission maybe omitted. In this case, data packets of the UE 1 is encrypted anddecrypted by the UE 1 and CN 3 (e.g., MME, C-SGN) by using NAS securitykeys.

In contrast to this, the second communication architecture type can bereferred to as “AS context caching” or “User Plane CIoT EPSoptimisation”. That is, in the second communication architecture type,user data packets transmitted or received by the UE 1 are transferredthrough the user plane (e.g., an EPS bearer including a DRB and aGeneral Packet Radio Service (GPRS) tunneling protocol (GTP) tunnel),and it involves suspension and resumption of an RRC connection.

The suspension of an RRC connection includes retaining, in the UE 1 andRAN 2 (e.g., eNB, CIoT-BS), information (or a context) of a previous RRCconnection while the UE 1 is in an RRC idle state (specifically, a newRRC state for CIoT (e.g., CIoT RRC-Idle state)). As already described,the context retained in the UE 1 and the RAN 2 includes, for example, anAccess Stratum Security Context, bearer-related information (incl. RoHCstate information), and L2/1 parameters when applicable. The RAN 2 mayinstruct the UE 1 to suspend an RRC connection using an RRC message(e.g., RRC Connection Release). Further, the RAN 2 may transmit terminalidentification information (e.g., Resume ID) used for resuming the RRCconnection, using this RRC message.

Further, the suspension of an RRC connection includes retaining, in theRAN 2 (e.g., eNB, CIoT-BS) and the CN 3 (e.g., MME, C-SGN), a signalingassociation regarding the UE 1 between the RAN 2 and the CN 3 while theUE 1 is in the RRC idle state (and also in the ECM-IDLE state). Thissignaling association regarding the UE 1 is an S1AP association. The RAN2 and the CN 3 retain this S1AP association and UE Contexts (e.g., eNBUE S1AP ID and MME UE S1AP ID) associated therewith. Furthermore, thesuspension of an RRC connection includes retaining, in the RAN 2 (e.g.,eNB, CIoT-BS) and the CN 3 (e.g., S-GW), a bearer context regarding adata bearer between the RAN 2 and the CN 3 while the UE 1 is in the RRCidle state (and also in the ECM-IDLE state). This data bearer is an S1-Ubearer, and this bearer context includes S1-U tunnel addresses (i.e., anS1 eNB tunnel endpoint identifier (TEID) and an S1 S-GW TEID).

The resumption of an RRC connection includes reusing the retained RRCconnection context by the UE 1 and the RAN 2 (e.g., eNB, CIoT-BS) for asubsequent RRC connection setup in order for the UE 1 to transition fromthe RRC idle state to the RRC connected state. Furthermore, theresumption of an RRC connection includes reusing or restoring theretained S1AP signaling association and the bearer context along with asubsequent RRC connection setup for the UE 1 to transition from the RRCidle state to the RRC connected state.

More specifically, when the UE 1 returns to the RRC-Connected mode, theUE 1 transmits an RRC Connection Resume Request to the RAN 2 (e.g.,eNB). The RAN 2 restores a DRB(s), a security context, an S1APconnection, and an S1-U tunnel(s) based on the retained context.Further, the RAN 2 informs the CN 3 of a UE state change using a newS1AP message (e.g., S1AP: UE Context Resume Request). A control planenode (e.g., MME) in the CN 3 returns the ECM state of the UE 1 to theECM-Connected state and transmits a Modify Bearer Request message to auser plane node (e.g., S-GW). As a result, the user plane noderecognizes that the UE 1 is in the connected state and hence becomesready to transmit downlink data towards the UE 1. Note that, the RRCmessage transmitted by the UE 1 for resuming the RRC connection may bean RRC Connection Resume Request. Alternatively, an RRC ConnectionRequest or an RRC Connection Reestablishment Request defined in LTE maybe reused for the RRC connection resume procedure. In the latter case, anew information element (IE) indicating a request for resumption of anRRC connection may be defined, and an RRC Connection Request or an RRCConnection Reestablishment Request may include this IE to indicate thatit is an RRC Connection Resume Request.

In this embodiment, the UE 1 is adapted to be configured by the networkto use both the first and second communication architecture types.

FIG. 3 is a sequence diagram showing an example of a communicationprocedure according to this embodiment. In the procedure of FIG. 3, inStep 301, the UE 1 is configured by the CN 3 (e.g., MME, C-SGN) to useboth the first communication architecture type (i.e., Solution 2) andthe second communication architecture type (i.e., Solution 18). Forexample, the UE 1 may include “Preferred Network Behaviour” in a NASmessage such as an Attach Request, a PDN Connection Request, and aTracking Area Update (TAU) Request. The Preferred Network Behaviourinforms the CN 3 (e.g., MME) about which of the first and secondcommunication architecture types the UE 1 would prefer to use (or whichof the first and second communication architecture types the UE 1supports). In consideration of “Preferred Network Behaviour”, the CN 3may determine the communication architecture type to be used (or allowedor configured) for the UE 1 and may inform the UE 1 of one or moredetermined communication architecture types using a NAS message (e.g.,Attach Accept, TAU Accept).

In Step 302, the UE 1 determines whether a specific (or pre-configured)criterion is met. In other words, in Step 302, the UE 1 detects (ordetermines) an occurrence of a request for specific data transmission.The pre-configured criterion or the request for specific datatransmission triggers the UE 1 to transmit data in accordance with thefirst communication architecture type (i.e., data transmission overNAS). In one example, the request for specific data transmission is arequest from a higher layer (e.g., service/application layer, IMS layer,NAS layer) to a lower layer (e.g., NAS layer, AS layer) (e.g., in thecase of Mobile Originated (MO) Access). Alternatively, the request forspecific data transmission may be a request from a lower layer (e.g., ASlayer) to a higher layer (e.g., NAS layer) (e.g., in the case of paging(Mobile Terminated (MT) Access). For example, the NAS layer of the UE 1may determine whether the request for specific data transmission hasbeen received from the higher layer (e.g., service/application layer,IMS layer) or the AS layer. Alternatively, the AS layer of the UE 1 maydetermine whether the request for specific data transmission has beenreceived from the NAS layer.

In response to the occurrence of a request for specific datatransmission when the UE 1 has already been configured by the CN 3 touse the first and second communication architecture types, the UE 1transmits data using the first communication architecture type.Specifically, in Step 303, the NAS layer of the UE 1 initiates a DoNASprocedure for transmitting data on the NAS layer. In Step 304, the UE 1generates a NAS message carrying small data and transmits an RRC message(e.g., RRC Connection Setup Complete, RRC Connection Resume Request, RRCConnection Resume Complete) containing this NAS message to the RAN 2(e.g., CIoT-BS, eNB).

In Step 305, the RAN 2 receives the RRC message and sends the NASmessage retrieved from the RRC message to the CN 3 using an SLAP message(e.g., Initial UE Message, UE Context Resume Request) (e.g., C-SGN,MME). The NAS message is embedded into an NAS-Protocol Data Unit (PDU)information element (IE) of this S1AP message. The RAN 2 may select,from DCNs in the CN 3, a DCN corresponding to the first communicationarchitecture type and send the S1AP message to the selected DCN.

In Step 306, the CN 3 (e.g., C-SGN, MME) decrypts the uplink NAS messagesent from the UE 1 to obtain the small data. The CN 3 forwards the smalldata to another node, entity, or network according to the data type ofthe small data.

In the example of FIG. 3, the specific data transmission may be aspecific type of small data transmission. For example, the specific datatransmission may be non-IP data transmission, SMS data transmission,(IP) data transmission of only one packet, or data transmission relatedto a predetermined service. It may be preferable for these types of datato be transferred over the control plane, rather than the user plane,because the amount thereof is small or it is not IP data.

According to the example of FIG. 3, when the UE 1 has already beenconfigured by the CN 3 to use the second communication architecturetype, the UE 1 can use the first communication architecture type for thetransmission of specific types of data that are well suited to thetransmission over the control plane. Thus, the UE 1 can effectivelyperform communication of the first communication architecture type whenthe UE 1 has already been configured by the CN 3 to use the secondcommunication architecture type.

Specifically, when the UE 1 has been configured by the CN 3 to use boththe first and second communication architecture types, the UE 1determines which of the first and second communication architecturetypes is to be used, depending on whether the requested communication isthe specific data transmission. This allows the UE 1 to properly performthe selection of the communication architecture type to be used when theUE 1 has been configured with two or more communication architecturetypes.

Second Embodiment

In this embodiment, a configuration example of a radio communicationnetwork is similar to that in FIG. 2. The UE 1 according to thisembodiment may be a CIoT device (e.g., NB-IoT, LTE eMTC), or may beanother UE in LTE, LTE-Advanced, or modified versions thereof.

FIG. 4 is a sequence diagram showing an example of a communicationprocedure according to this embodiment. Similarly to the procedure ofFIG. 3, in the procedure of FIG. 4, in Step 401, the UE 1 is configuredby the CN 3 (e.g., MME, C-SGN) to use both the first communicationarchitecture type (i.e., Solution 2) and the second communicationarchitecture type (i.e., Solution 18). Further, in Step 401, the UE 1executes a suspension operation for the second communicationarchitecture type. That is, the UE 1 retains a context regarding aprevious RRC connection while the UE 1 is in the RRC idle state (e.g.,CIoT RRC idle state).

In Step 402, data transmission in accordance with the firstcommunication architecture type is triggered. That is, the UE 1 detects(or determines) an occurrence of a request for data transmission inaccordance with the first communication architecture type while the UE 1is executing the suspension operation for the second communicationarchitecture type. As described in the first embodiment, the request fordata transmission is sent from a higher layer (e.g., service/applicationlayer, IMS layer, NAS layer) to a lower layer (e.g., NAS layer, ASlayer), or sent from a lower layer (e.g., AS layer) to a higher layer(e.g., NAS layer). In the example of FIG. 4, the UE 1 is triggered forSMS transmission. Note that the SMS transmission is merely an example oftransmission suitable for the first communication architecture type. Asdescribed in the first embodiment, in Step 402, the UE 1 may betriggered for non-IP data transmission, (IP) data transmission of onlyone packet, or data transmission related to a predetermined service.

In Step 403, in response to the occurrence of a request for datatransmission in accordance with the first communication architecturetype (e.g., SMS transmission) while the UE 1 is executing the suspensionoperation for the second communication architecture type, the UE 1initiates communication in accordance with the first communicationarchitecture type (i.e., data transmission over NAS) while retaining theprevious RRC connection context. In the specific example shown in FIG.4, the NAS layer of the UE 1 performs an RRC Connection Resume procedurefor resuming an RRC connection (Steps 404 to 406).

In Steps 404 to 406, the RRC connection is resumed. Specifically, inStep 404, the UE 1 transmits an RRC Connection Resume Request message tothe RAN 2 (e.g., eNB, CIoT-BS). The RRC Connection Resume Requestmessage contains a resume ID. This resume ID is, for example, acombination of a Cell-Radio Network Temporary Identifier (C-RNTI) and aCell ID (e.g., Physical Cell ID (PCI)). In FIG. 4, a representation ofthe random access procedure is omitted. The RRC Connection ResumeRequest message of Step 404 may be transmitted in the third message (Msg3) of the random access procedure.

The RAN 2 receives the RRC Connection Resume Request message, obtainsthe resume ID from the RRC Connection Resume Request message, andresumes the RRC connection based on the retained context associated withthis resume ID. In Step 405, the RAN 2 transmits an RRC ConnectionResume message to the UE 1. This RRC Connection Resume messageindicates, for example, which DRB(s) is resumed. This RRC ConnectionResume message may include L2/L1 parameters. The UE 1 resumes theretained AS security context according to the RRC Connection Resumemessage of Step 405. In Step 406, the UE 1 transmits an RRC ConnectionResume Complete message to the RAN 2.

The RRC connection resume procedure shown in Steps 404 to 406 is merelyan example. For example, although Steps 404 to 406 show a resumeprocedure including three steps (or three messages), the RRC connectionresume procedure may be performed by two steps (two messages). In thiscase, the transmission from the UE 1 to the RAN 2 in Step 406 may beomitted. Further, the message from the RAN 2 to the UE 1 in Step 405 maybe referred to as a RRC Connection Resume Complete message. Further, theRRC Connection Resume Request, RRC Connection Resume, and RRC ConnectionResume Complete in the RRC connection resume procedure shown in theSteps 404 to 406 may be replaced with an RRC Connection Request (or RRCConnection Reestablishment Request), an RRC Connection Setup (or RRCConnection Reestablishment), and an RRC Connection Setup Complete (orRRC Connection Reestablishment Complete), respectively.

In Steps 407 to 409, the S1AP association and the S1-U bearer(s) for theUE 1 are resumed. In Step 407, the RAN 2 informs the CN 3 (e.g., MME,C-SGN) about a state change of the UE 1 using a new S1AP message (e.g.,S1AP: UE Context Resume Request). The CN 3 returns the ECM state of theUE 1 to the ECM-Connected state and transmits a Modify Bearer Requestmessage to the S/P-GW 6 (Step 408). The S/P-GW 6 then recognizes thatthe UE 1 is in the connected state and becomes ready to transmitdownlink data towards the UE 1. In Step 409, the CN 3 sends, to the RAN2, a response message (e.g., S1AP: UE Context Resume Response)indicating the completion of the resumption of the S1AP association andS1-U bearer(s) for the UE 1.

In Step 410, the NAS layer of the UE 1 initiates a DoNAS procedure fortransmitting data on the NAS layer. In Step 411, the UE 1 generates aNAS message carrying small data (e.g., SMS data) and transmits an RRCmessage (e.g., UL Information Transfer) containing this NAS message tothe RAN 2 (e.g., eNB, CIoT-BS). As already described, at the presenttime, it is assumed that neither the solution 2 nor the solution 18 willuse SRB 2. Thus, the RRC message of Step 411 may be transmitted usingSRB 1 on a Dedicated Control Channel (DCCH).

In Step 412, the RAN 2 receives the RRC message and sends the NASmessage retrieved from the RRC message to the CN 3 (e.g., C-SGN, MME)using an S1AP message (e.g., Uplink NAS Transport). The NAS message isembedded into a NAS-Protocol Data Unit (PDU) information element (IE) ofthe S1AP message. The RAN 2 may select, from DCNs in the CN 3, a DCNcorresponding to the first communication architecture type and send theS1AP message to the selected DCN.

In Step 413, the CN 3 (e.g., MME, C-SGN) decrypts the uplink NAS messagesent from the UE 1 to obtain the small data. The CN 3 forwards the smalldata packet to another node, entity, or network, according to the datatype of the small data. In the example of FIG. 4, the CN 3 sends theobtained SMS data to an entity related to SMS (e.g., SMS-GMSC,SMS-IWMSC, SMS router).

As can be understood from the above description, in the example of FIG.4, in response to an occurrence of a request for data transmission inaccordance with the first communication architecture type (e.g., SMStransmission) while the UE 1 is executing the suspension operation forthe second communication architecture type, the UE 1 initiatescommunication in accordance with the first communication architecturetype (i.e., data transmission over NAS) while retaining the previous RRCconnection context. Thus, even when the data transmission over NASoccurs while the UE 1 is executing the suspension operation for thesecond communication architecture type, the UE 1 can be continuing thesuspension operation for the second communication architecture type.

In the example of FIG. 4, in order to perform the communication of thefirst communication architecture type, the UE 1 transmits to the RAN 2RRC messages (e.g., RRC Connection Resume Request, RRC Connection ResumeComplete) that are used for resuming the RRC connection in the RRCconnection resume procedure (Steps 404 to 406). The UE 1 may include anindication of DoNAS transmission in any one or all of these uplink RRCmessages. Additionally or alternatively, the UE 1 may include anindication of DoNAS transmission in the NAS message carrying small data(e.g., SMS data).

Additionally or alternatively, the UE 1 may include information about abuffer volume (i.e., buffer status) in any one or all of these uplinkRRC messages. The information about the buffer volume is newly definedfor communication for DoNAS, namely, for transmitting information overthe control plane (i.e., SRB). The information about the buffer volumeindicates a buffer volume regarding a bearer that is not yet establishedand also indicates a buffer volume regarding data to be transmitted onan SRB. That is, the information about the buffer volume differs fromthe Buffer Status Report (BSR), which has been defined in LTE and is tobe carried by an MAC Control Element (MAC CE). Thus, the RRC messagecontaining the information about the buffer volume can indicate DoNAStransmission.

Additionally or alternatively, radio resources (e.g., time, frequency,preamble index pool) used for random access preamble transmission may bedistinguished in advance between the first communication architecturetype and the second communication architecture. In this case, the RAN 2can determine whether it is intended for DoNAS transmission, dependingon which radio resource is used.

According to these techniques, the RAN 2 can recognize that the RRCconnection resume procedure is intended for DoNAS. Further, the RAN 2may explicitly inform the CN 3 that the RRC connection resume procedureis intended for DoNAS transmission (e.g., Selected CIoT EPSoptimization). Additionally or alternatively, the RAN 2 (or the UE 1)may include, in the NAS information (e.g., NAS Control PDU), informationexplicitly or implicitly indicating that the RRC connection resumeprocedure is intended for DoNAS (e.g., Preferred Network Behaviour). Amethod for an implicit indication may include, for example, setting allbearer IDs (e.g., E-RAB IDs) included in an E-RAB To Be Resumed List IEindicating bearer(s) to be resumed to an invalid value or 0, blankingthe E-RAB To Be Resumed List IE, or including E-RAB IDs of allestablished (i.e., suspended) bearers in the E-RAB Failed To Resume ListIE. This allows the CN 3 to recognize that the RRC connection resumeprocedure is intended for DoNAS. Thus, for example, the RAN 2 and CN 3can operate such that they do not perform signaling (Steps 408 and 409)to resume the S1-U bearer(s) that is not required for the DoNAStransmission.

In some implementations, the UE 1 may include an establishment causeassociated with DoNAS or a resume cause associated with DoNAS in the RRCConnection Resume Request (Step 404). The UE 1 may include theestablishment cause associated with DoNAS or the resume cause associatedwith DoNAS in the RRC Connection Resume Complete (Step 406). Theestablishment cause or resume cause may be defined as “mo-Data-DoNAS”.Alternatively, the UE 1 may include information (e.g., 1-bit flag)indicating whether the communication is intended for DoNAS in the resumeID. In these ways, the RAN 2 can recognize that the RRC connectionresume procedure (Steps 404 to 406) is performed for DoNAS. The RAN 2may include the establishment cause associated with DoNAS, the resumecause associated with DoNAS, or an information element corresponding tothem in the S1AP message of Step 407. This allows the RAN 2 to informthe CN 3 that the resumption of the S1-U bearer(s) is not required.

Furthermore, in the procedure of FIG. 4, to facilitate the interactionbetween the NAS layer and the AS layer (e.g., RRC layer) in the UE 1,the NAS layer of the UE 1 may operate as follows. Note that the NASlayer provides mobility management and session management, while the ASlayer provides radio resource control (RRC).

In the procedure of FIG. 4, the NAS layer of the UE 1 needs to requestthe AS layer to start the RRC Connection Resume procedure for the secondcommunication architecture type (i.e., AS Context Cashing) whilespecifying (or triggering) the execution of the first communicationarchitecture type (i.e., DoNAS). In order to achieve this, for example,when SMS data is transmitted in DoNAS, the NAS layer of the UE 1 maygenerate a NAS message carrying this SMS data and provide an RRCconnection establishment request to the AS layer. This RRC connectionestablishment request contains a call type (i.e., originating SMS)indicating SMS transmission from a mobile, and a new establishment causefor DoNAS (e.g., mo-Data-DoNAS).

Instead, when non-IP data is transmitted in DoNAS, the NAS layer of theUE 1 generates a NAS message carrying this non-IP data and provide anRRC connection establishment request to the AS layer. This RRCconnection establishment request contains a new call type (i.e.,originating Non-IP call) indicating non-IP data transmission from amobile, and a new establishment cause for DoNAS (e.g., mo-Data-DoNAS).

According to these operations, the AS layer of the UE 1 can recognizethat the RRC Connection Resume procedure for the second communicationarchitecture type (i.e., AS Context Cashing) is executed for the firstcommunication architecture type (i.e., DoNAS) based on the newcombination of the call type and the establishment cause.

Third Embodiment

In this embodiment, a configuration example of a radio communicationnetwork is similar to that in FIG. 2. The UE 1 according to thisembodiment may be a CIoT device (e.g., NB-IoT, LTE eMTC), or may beanother UE in LTE, LTE-Advanced, or modified versions thereof.

FIG. 5 is a sequence diagram showing an example of a communicationprocedure according to this embodiment. Steps 501 and 502 in FIG. 5 aresimilar to Steps 401 and 402 in FIG. 4, respectively. In Step 501, theUE 1 is configured by the CN 3 (e.g., MME, C-SGN) to use both the firstcommunication architecture type (i.e., Solution 2) and the secondcommunication architecture type (i.e., Solution 18). Furthermore, inStep 501, the UE 1 executes a suspension operation for the secondcommunication architecture type.

In Step 502, data transmission in accordance with the firstcommunication architecture type is triggered. That is, the UE 1 detects(or determines) an occurrence of a request for data transmission inaccordance with the first communication architecture type while the UE 1is executing the suspension operation for the second communicationarchitecture type. As described in the first embodiment, the request fordata transmission is sent from a higher layer (e.g., service/applicationlayer, IMS layer, NAS layer) to a lower layer (e.g., NAS layer, ASlayer), or sent from a lower layer (e.g., AS layer) to a higher layer(e.g., NAS layer). In the example of FIG. 5, the UE 1 is triggered forSMS transmission. Similarly to the description for Step 402, SMStransmission is merely an example of transmission suitable for the firstcommunication architecture type.

In Step 503, in response to the occurrence of a request for datatransmission in accordance with the first communication architecturetype (e.g., SMS transmission) while the UE 1 is executing the suspensionoperation for the second communication architecture type, the UE 1initiates communication in accordance with the first communicationarchitecture type (i.e., data transmission over NAS) while retaining theprevious RRC connection context. In the specific example shown in FIG.5, the NAS layer of the UE 1 performs an RRC Connection Resume procedurefor resuming an RRC connection and also performs a DoNAS transmissionprocedure (Steps 504 to 506). In other words, in the example of FIG. 5,the UE 1 performs the DoNAS transmission procedure that is integrated(or combined) with the RRC Connection Resume procedure.

In Steps 504 to 506, a NAS message carrying SMS data is transmitted fromthe UE 1 to the RAN 2 at the same time that the RRC connection isresumed. In Step 504, the UE 1 transmits an RRC Connection ResumeRequest message to the RAN 2 (e.g., eNB, CIoT-BS). In FIG. 5, arepresentation of the random access procedure is omitted. The RRCConnection Resume Request message of Step 504 may be transmitted in thethird message (Msg 3) of the random access procedure. In Step 505, theRAN 2 resumes the RRC connection and transmits an RRC Connection Resumemessage to the UE 1. In Step 506, the UE 1 transmits an RRC ConnectionResume Complete message to the RAN 2. The RRC Connection Resume Completemessage of Step 506 contains the NAS message carrying the SMS data.

In Steps 507 to 510, the NAS message carrying the SMS data istransmitted from the RAN 2 to the CN 3 at the same time that the S1APassociation and the S1-U bearer(s) for the UE 1 are resumed. In Step507, the RAN 2 informs the CN 3 (e.g., MME, C-SGN) about a state changeof the UE 1 using a new S1AP message (e.g., S1AP: UE Context ResumeRequest). The NAS-PDU in the S1AP message of Step 507 contains the NASmessage carrying the SMS data.

In Step 508, the CN 3 (e.g., MME, C-SGN) decrypts the uplink NAS messagesent from the UE 1 to obtain the small data. The CN 3 forwards the smalldata packet to another node, entity, or network, according to the datatype of the small data. In the example of FIG. 5, the CN 3 sends theobtained SMS data to an entity related to SMS (e.g., SMS-GMSC,SMS-IWMSC, SMS router).

Steps 509 and 510 are similar to Steps 408 and 409 in FIG. 4,respectively. The CN 3 returns the ECM state of the UE 1 to theECM-Connected state and transmits a Modify Bearer Request message to theS/P-GW 6 (Step 509). After that, the S/P-GW 6 recognizes that the UE 1is in the connected state and hence becomes ready to transmit downlinkdata towards the UE 1. In Step 510, the CN 3 sends, to the RAN 2, aresponse message (e.g., S1AP: UE Context Resume Response) indicating thecompletion of the resumption of the S1AP association and S1-U bearer(s)for the UE 1.

As can be understood from the above description, in the example of FIG.5, in response to an occurrence of a request for data transmission inaccordance with the first communication architecture type (e.g., SMStransmission) while the UE 1 is executing the suspension operation forthe second communication architecture type, the UE 1 initiatescommunication in accordance with the first communication architecturetype (i.e., data transmission over NAS) while retaining the previous RRCconnection context. Thus, similarly to the example of FIG. 4, even whenthe data transmission over NAS occurs while the UE 1 is executing thesuspension operation for the second communication architecture type, theUE 1 can be continuing the suspension operation for the secondcommunication architecture type.

Further, in the example of FIG. 5, the UE 1 performs the DoNAStransmission procedure that is integrated (or combined) with the RRCConnection Resume procedure. Thus, in the example of FIG. 5, the numberof signalings required for the DoNAS transmission can be reducedcompared with the example of FIG. 4.

Similarly to the example of FIG. 4, the RRC connection resume procedureshown in Steps 504 to 506 is merely an example. For example, thetransmission from the UE 1 to the RAN 2 in Step 506 may be omitted. Inthis case, the UE 1 may include the NAS message carrying the SMS data inthe RRC Connection Resume Request message of Step 504. For example, theRRC Connection Request (or the RRC Connection Reestablishment Request),the RRC Connection Setup (or the RRC Connection Reestablishment), andthe RRC Connection Setup Complete (or the RRC Connection ReestablishmentComplete) may be reused for the RRC connection resume procedure in Steps504 to 506.

Further, similarly to the example of FIG. 4, in the example of FIG. 5,the UE 1 may include an indication of DoNAS transmission in any one orall of these uplink RRC messages (Steps 504 and 506). Additionally oralternatively, the UE 1 may include an indication of DoNAS transmissionin the NAS message carrying small data (e.g., SMS data). Additionally oralternatively, the UE 1 may include information about a buffer volume(i.e., buffer status) in any one or all of these uplink RRC messages.Additionally or alternatively, radio resources (e.g., time, frequency,preamble index pool) used for random access preamble transmission may bedistinguished in advance between the first communication architecturetype and the second communication architecture. According to thesetechniques, the RAN 2, or the CN 3, or both can recognize that the RRCconnection resume procedure is intended for DoNAS. Thus, for example,the RAN 2 and CN 3 can operate such that they do not perform signaling(Steps 509 and 510) to resume the S1-U bearer(s) that is not requiredfor the DoNAS transmission.

Further, similarly to the example of FIG. 4, in the example of FIG. 5,when SMS data is transmitted in DoNAS, the NAS layer of the UE 1 maygenerate a NAS message carrying this SMS data and provide an RRCconnection establishment request to the AS layer. This RRC connectionestablishment request contains a call type (i.e., originating SMS)indicating SMS transmission from a mobile, and a new establishment causefor DoNAS (e.g., mo-Data-DoNAS). Further, when non-IP data istransmitted in DoNAS, the NAS layer of the UE 1 may generate a NASmessage carrying this non-IP data and provide an RRC connectionestablishment request to the AS layer. This RRC connection establishmentrequest contains a new call type (i.e., originating Non-IP call)indicating non-IP data transmission from a mobile, and a newestablishment cause for DoNAS (e.g., mo-Data-DoNAS).

Fourth Embodiment

In this embodiment, a configuration example of a radio communicationnetwork is similar to that in FIG. 2. The UE 1 according to thisembodiment may be a CIoT device (e.g., NB-IoT, LTE eMTC), or may beanother UE in LTE, LTE-Advanced, or modified versions thereof.

FIG. 6 is a sequence diagram showing an example of a communicationprocedure according to this embodiment. The procedure of FIG. 6 issimilar to the above-described procedure of FIG. 5. However, in theprocedure of FIG. 6, an RRC connection establishment procedure (Steps604 to 606) is used for DoNAS data transmission, instead of the RRCconnection resume procedure (Steps 504 to 506 in FIG. 5).

Steps 601 and 602 in FIG. 6 are similar to Steps 501 and 502 in FIG. 5,respectively. In Step 601, the UE 1 is configured by the CN 3 (e.g.,MME, C-SGN) to use both the first communication architecture type (i.e.,Solution 2) and the second communication architecture type (i.e.,Solution 18). Furthermore, in Step 501, the UE 1 executes the suspensionoperation for the second communication architecture type.

In Step 602, data transmission in accordance with the firstcommunication architecture type is triggered. That is, the UE 1 detects(or determines) an occurrence of a request for data transmission inaccordance with the first communication architecture type while the UE 1is executing the suspension operation for the second communicationarchitecture type. As described in the first embodiment, the request fordata transmission is sent from a higher layer (e.g., service/applicationlayer, IMS layer, NAS layer) to a lower layer (e.g., NAS layer, ASlayer), or sent from a lower layer (e.g., AS layer) to a higher layer(e.g., NAS layer). In the example of FIG. 6, the UE 1 is triggered forSMS transmission. Similarly to the description for Steps 402 and 502,SMS transmission is merely an example of transmission suitable for thefirst communication architecture type.

In Step 603, in response to the occurrence of a request for datatransmission in accordance with the first communication architecturetype (e.g., SMS transmission) while the UE 1 is executing the suspensionoperation for the second communication architecture type, the UE 1initiates communication in accordance with the first communicationarchitecture type (i.e., data transmission over NAS) while retaining theprevious RRC connection context. In the example shown in FIG. 6, the NASlayer of the UE 1 performs the DoNAS transmission procedure that isintegrated (or combined) with the RRC connection establishment procedure(Steps 604 to 606).

In Steps 604 to 606, a NAS message carrying the SMS data is transmittedfrom the UE 1 to the RAN 2 at the same time that the RRC connection isestablished. In Step 604, the UE 1 transmits an RRC Connection Requestmessage to the RAN 2 (e.g., eNB, CIoT-BS). In FIG. 6, a representationof the random access procedure is omitted. The RRC Connection Requestmessage of Step 604 may be transmitted in the third message (Msg 3) ofthe random access procedure. In Step 605, the RAN 2 transmits an RRCConnection Setup message to the UE 1. In Step 606, the UE 1 transmits anRRC Connection Setup Complete message to the RAN 2. The RRC ConnectionSetup Complete message of Step 506 contains the NAS message carrying SMSdata.

In Step 607, the RAN 2 sends the NAS message carrying the SMS data tothe CN 3 (e.g., MME, C-SGN) using an S1AP message (e.g., Initial UEMessage). The NAS-PDU in the S1AP message of Step 607 contains the NASmessage carrying the SMS data. The RAN 2 may select, from DCNs in the CN3, a DCN corresponding to the first communication architecture type andsend the S1AP message to the selected DCN.

In Step 608, the CN 3 (e.g., MME, C-SGN) decrypts the uplink NAS messagesent from the UE 1 to obtain the small data. The CN 3 forwards the smalldata packet to another node, entity, or network, according to the datatype of the small data. In the example of FIG. 6, the CN 3 sends theobtained SMS data to an entity related to SMS (e.g., SMS-GMSC,SMS-IWMSC, SMS router).

As can be understood from the above description, in the example of FIG.6, in response to an occurrence of a request for data transmission inaccordance with the first communication architecture type (e.g., SMStransmission) while the UE 1 is executing the suspension operation forthe second communication architecture type, the UE 1 initiatescommunication in accordance with the first communication architecturetype (i.e., data transmission over NAS) while retaining the previous RRCconnection context. Thus, similarly to the example of FIGS. 4 and 5,even when the data transmission over NAS occurs while the UE 1 isexecuting the suspension operation for the second communicationarchitecture type, the UE 1 can be continuing the suspension operationfor the second communication architecture type.

Further, in the example shown in FIG. 6, the UE 1 performs the DoNAStransmission procedure that is integrated (or combined) with the RRCconnection establishment procedure. Thus, in the example of FIG. 6, thenumber of signalings required for the DoNAS transmission can be reducedcompared with the example of FIG. 4.

Further, similarly to the example of FIG. 4, in the example of FIG. 6,the UE 1 may include an indication of DoNAS transmission in any one orall of these uplink RRC messages (Steps 604 and 606). Additionally oralternatively, the UE 1 may include an indication of DoNAS transmissionin the NAS message carrying small data (e.g., SMS data). Additionally oralternatively, the UE 1 may include information about a buffer volume(i.e., buffer status) in any one or all of these uplink RRC messages.Additionally or alternatively, radio resources (e.g., time, frequency,preamble index pool) used for random access preamble transmission may bedistinguished in advance between the first communication architecturetype and the second communication architecture. According to thesetechniques, the RAN 2, or the CN 3, or both can recognize that the RRCconnection resume procedure is intended for DoNAS.

Further, similarly to the example of FIG. 4, in the example of FIG. 6,when SMS data is transmitted in DoNAS, the NAS layer of the UE 1 maygenerate a NAS message carrying this SMS data and provide an RRCconnection establishment request to the AS layer. This RRC connectionestablishment request contains a call type (i.e., originating SMS)indicating SMS transmission from a mobile, and a new establishment causefor DoNAS (e.g., mo-Data-DoNAS). Further, when non-IP data istransmitted in DoNAS, the NAS layer of the UE 1 may generate a NASmessage carrying this non-IP data and provide an RRC connectionestablishment request to the AS layer. This RRC connection establishmentrequest contains a new call type (i.e., originating Non-IP call)indicating non-IP data transmission from a mobile, and a newestablishment cause for DoNAS (e.g., mo-Data-DoNAS).

The above description about this embodiment shows an example in which,when the UE 1 is executing the suspension operation for the secondcommunication architecture type, it initiates communication inaccordance with the first communication architecture type whileretaining the previous RRC connection context. Upon ending thecommunication in accordance with the first communication architecturetype, the UE 1 may transition to the RRC-Idle mode again, and thenresume the RRC connection using this RRC connection context to transmitdata in accordance with the second communication architecture type.

Alternatively, in this embodiment, the UE 1 may release (or discard) theprevious RRC connection context when establishing the RRC connection totransmit data in accordance with the first communication architecturetype.

Fifth Embodiment

In this embodiment, a configuration example of a radio communicationnetwork is similar to that in FIG. 2. The UE 1 according to thisembodiment may be a CIoT device (e.g., NB-IoT, LTE eMTC), or may beanother UE in LTE, LTE-Advanced, or modified versions thereof.

FIG. 7 is a sequence diagram showing an example of a communicationprocedure according to this embodiment. The procedure of FIG. 7 shows anexample in which the UE 1 is configured by the CN 3 (e.g., MME, C-SGN)to use both the first and second communication architecture types andperforms DoNAS transmission while the UE 1 is in the RRC Connectedstate.

In Step 701, the UE 1 is configured by the CN 3 (e.g., MME, C-SGN) touse both the first communication architecture type (i.e., Solution 2)and the second communication architecture type (i.e., Solution 18). InStep 702, when the UE 1 is in the RRC_Connected state, data transmissionin accordance with the first communication architecture type istriggered. That is, the UE 1 detects (or determines) an occurrence of arequest for data transmission in accordance with the first communicationarchitecture type while the UE 1 is obeying the second communicationarchitecture type and is in the RRC_Connected state. As described in thefirst embodiment, the request for data transmission is sent from ahigher layer (e.g., service/application layer, IMS layer, NAS layer) toa lower layer (e.g., NAS layer, AS layer), or sent from a lower layer(e.g., AS layer) to a higher layer (e.g., NAS layer).

In Step 703, in response to the occurrence of a request for datatransmission in accordance with the first communication architecturetype (e.g., SMS transmission) while the UE 1 is obeying the secondcommunication architecture type and in the RRC_Connected state, the NASlayer of the UE 1 initiates communication in accordance with the firstcommunication architecture type (i.e., data transmission over NAS). InStep 704, in response to a request from the NAS layer of the UE 1, theAS layer of the UE 1 performs the random access procedure and transmitsto the RAN 2 (e.g., eNB, CIoT-BS) a DoNAS request in the third message(Msg 3) of the random access procedure.

In Step 705, the RAN 2 transmits an uplink (UL) grant to the UE 1 inresponse to receiving the DoNAS request. The UL grant indicatesallocation of uplink radio resources to enable the UE 1 to transmit aNAS message for DoNAS. In Step 706, the UE 1 transmits an RRC message(e.g., UL Information Transfer) containing a NAS message carrying SMSdata to the RAN 2 according to the UL grant (Step 706). As alreadydescribed, at the present time, it is assumed that neither the solution2 nor the solution 18 will use SRB 2. Thus, the RRC message of Step 706may be transmitted using SRB 1 on a Dedicated Control Channel (DCCH).

In Step 707, the RAN 2 sends the NAS message retrieved from the RRCmessage of Step 706 to the CN 3 (e.g., C-SGN, MME) using an S1AP message(e.g., Uplink NAS Transport). The NAS message is embedded in aNAS-Protocol Data Unit (PDU) information element (IE) of this S1APmessage. The RAN 2 may select, from DCNs in the CN 3, a DCNcorresponding to the first communication architecture type from withinthe CN 3 and send the S1AP message to the selected DCN.

In Step 708, the CN 3 (e.g., MME, C-SGN) decrypts the uplink NAS messagefrom the UE 1 to obtain the small data. The CN 3 forwards the small datapacket to another node, entity, or network, according to the data typeof the small data. In the example of FIG. 7, the CN 3 sends the obtainedSMS data to an entity related to SMS (e.g., SMS-GMSC, SMS-IWMSC, SMSrouter).

As can be understood from the above description, in the example of FIG.7, when the UE 1 has been configured by the CN 3 to use the first andsecond communication architecture types and is in the RRC Connectedstate, the UE 1 can use the first communication architecture type totransmit specific types of data that are well suited to the transmissionover the control plane.

In some implementations, the DoNAS request transmitted in Step 704 ofFIG. 7 may be transmitted on a Physical Uplink Control Channel (PUCCH).The DONAS request may be carried by an Uplink Control Information (UCI)format newly defined or modified for the DoNAS request. When the UE 1has available PUCCH resources, the UE 1 may transmit the DoNAS requestover a PUCCH without performing the random access procedure.

In some implementations, the DoNAS request transmitted in Step 704 ofFIG. 7 may be transmitted using an RRC message. This RRC message mayindicate the establishment cause associated with DoNAS. Likewise, theRRC message (e.g., UL Information Transfer) in Step 706 may indicate theestablishment cause associated with DoNAS.

Sixth Embodiment

In this embodiment, a configuration example of a radio communicationnetwork is similar to that in FIG. 2. The UE 1 according to thisembodiment may be a CIoT device (e.g., NB-IoT, LTE eMTC), or may beanother UE in LTE, LTE-Advanced, or modified versions thereof.

In this embodiment, the UE 1 is configured by the CN 3 to use either ofthe first and second communication architecture types and not tosimultaneously use both the first and second communication architecturetypes.

FIG. 8 is a sequence diagram showing an example of a communicationprocedure according to this embodiment. In the procedure of FIG. 8, inStep 801, the UE 1 is configured by the CN 3 (e.g., MME, C-SGN) to useonly the second communication architecture type (i.e., Solution 18). TheCN 3 may permit the UE 1 to use the first communication architecturetype (i.e., Solution 2) when a pre-configured criterion is met.

In Step 802, the UE 1 determines that the pre-configured criterion ismet. In other words, in Step 802, the NAS layer of the UE 1 determineswhether a request for specific data transmission has been received froma higher layer (e.g., service/application layer, IMS layer). Thepre-configured criterion or the request for specific data transmissiontriggers the UE 1 to transmit data in accordance with the firstcommunication architecture type (i.e., data transmission over NAS).

In response to the occurrence of a request for specific datatransmission when the UE 1 has already been configured by the CN 3 touse the second communication architecture type, the UE 1 switches fromthe second communication architecture type to the first communicationarchitecture type and transmits data using the first communicationarchitecture type. The procedure for the data transmission in accordancewith the first communication architecture type may be similar to theMobile Originated (MO) small data transmission procedure for thesolution 2 (i.e., DoNAS) disclosed in Non Patent Literature 1.

That is, in Step 803, the NAS layer of the UE 1 initiates a DoNASprocedure for transmitting data on the NAS layer. In Step 804, the UE 1generates a NAS message carrying small data and transmits an RRC message(e.g., RRC Connection Setup Complete, UL Information Transfer)containing this NAS message to the RAN 2 (e.g., CIoT-BS, eNB).

In Step 805, the RAN 2 receives the RRC message and sends the NASmessage retrieved from the RRC message to the CN 3 (e.g., C-SGN, MME)using an S1AP message (e.g., Initial UE Message, Uplink NAS Transport).The NAS message is embedded into a NAS-Protocol Data Unit (PDU)information element (IE) of this S1AP message. The RAN 2 may select,from DCNs in the CN 3, a DCN corresponding to the first communicationarchitecture type and send the S1AP message to the selected DCN.

In Step 806, the CN 3 (e.g., C-SGN, MME) decrypts the uplink NAS messagesent from the UE 1 to obtain the small data. The CN 3 forwards the smalldata to another node, entity, or network, according to the data type ofthe small data.

In the example of FIG. 8, the specific data transmission may be similarto that of the example of FIG. 3 described in the first embodiment. Forexample, the specific data transmission may be non-IP data transmission,SMS data transmission, (IP) data transmission of only one packet, ordata transmission related to a predetermined service.

According to the example of FIG. 8, when the UE 1 has already beenconfigured by the CN 3 to use the second communication architecturetype, the UE 1 can use the first communication architecture type totransmit specific types of data that are well suited to the transmissionover the control plane. Thus, the UE 1 can effectively performcommunication in accordance with the first communication architecturetype when the UE 1 has already been configured by the CN 3 to use thesecond communication architecture type.

Specifically, in response to an occurrence of a request for specificdata transmission when the UE 1 has already been configured by the CN 3to use only the second communication architecture type, the UE 1switches from the second communication architecture type to the firstcommunication architecture type. That is, the UE 1 is configured withonly one of the first and second communication architecture types andthus it does not need to support a simultaneous setup of these twosolutions. This simplifies the configuration of the UE 1. Such aconfiguration is particularly effective for NB-CIoT that requires costoptimization and low power consumption.

Seventh Embodiment

In this embodiment, a configuration example of a radio communicationnetwork is similar to that in FIG. 2. The UE 1 according to thisembodiment may be a CIoT device (e.g., NB-IoT, LTE eMTC), or may beanother UE in LTE, LTE-Advanced, or modified versions thereof.

FIG. 9 is a sequence diagram showing an example of a communicationprocedure according to this embodiment. Similarly to the procedure ofFIG. 8, in the procedure of FIG. 9, in Step 901, the UE 1 is configuredby the CN 3 (e.g., MME, C-SGN) to use only the second communicationarchitecture type (i.e., Solution 18). The CN 3 may permit the UE 1 touse the first communication architecture type (i.e., Solution 2) when aspecific criterion is met. In Step 901, the UE 1 performs a suspensionoperation for the second communication architecture type. Specifically,the UE 1 retains a context regarding a previous RRC connection while itis in the RRC idle state (e.g., CIoT RRC idle state).

In Step 902, data transmission in accordance with the firstcommunication architecture type is triggered. That is, the UE 1 detects(or determines) an occurrence of a request for data transmission inaccordance with the first communication architecture type while the UE 1is executing the suspension operation for the second communicationarchitecture type. As described in the first embodiment, the request fordata transmission is sent from a higher layer (e.g., service/applicationlayer, IMS layer, NAS layer) to a lower layer (e.g., NAS layer, ASlayer), or sent from a lower layer (e.g., AS layer) to a higher layer(e.g., NAS layer). In the example of FIG. 9, the UE 1 is triggered forSMS transmission. Note that the SMS transmission is merely an example oftransmission suitable for the first communication architecture type. Asdescribed in the first embodiment, in Step 902, the UE 1 may betriggered for non-IP data transmission, (IP) data transmission of onlyone packet, or data transmission related to a predetermined service.

In Step 903, in response to the occurrence of a request for datatransmission in accordance with the first communication architecturetype (e.g., SMS transmission) while the UE 1 is executing the suspensionoperation for the second communication architecture type, the UE 1switches from the second communication architecture type to the firstcommunication architecture type and initiates communication inaccordance with the first communication architecture type (i.e., datatransmission over NAS). The procedure for the data transmission inaccordance with the first communication architecture type may be similarto the Mobile Originated (MO) small data transmission procedure for thesolution 2 (i.e., DoNAS) disclosed in Non Patent Literature 1.

That is, in Steps 904 to 906, the UE 1 executes an RRC connectionestablishment procedure. In Steps 904 to 906, a NAS message carrying SMSdata is transmitted from the UE 1 to the RAN 2 at the same time that theRRC connection is established. In Step 904, the UE 1 transmits an RRCConnection Request message to the RAN 2 (e.g., eNB, CIoT-BS). In FIG. 9,a representation of the random access procedure is omitted. The RRCConnection Request message of Step 904 may be transmitted in the thirdmessage (Msg 3) of the random access procedure. In Step 905, the RAN 2transmits an RRC Connection Setup message to the UE 1. In Step 906, theUE 1 transmits an RRC Connection Setup Complete message to the RAN 2.The RRC Connection Setup Complete message of Step 906 contains the NASmessage carrying SMS data.

In Step 907, the RAN 2 sends the NAS message carrying the SMS data tothe CN 3 (e.g., MME, C-SGN) using an S1AP message (e.g., Initial UEMessage). The NAS-PDU in the S1AP message of Step 907 contains the NASmessage carrying the SMS data. The RAN 2 may select, from DCNs in the CN3, a DCN corresponding to the first communication architecture type andsend the S1AP message to the selected DCN.

In Step 908, the CN 3 (e.g., MME, C-SGN) decrypts the uplink NAS messagesent from the UE 1 to obtain the small data. The CN 3 forwards the smalldata packet to another node, entity, or network, according to the datatype of the small data. In the example of FIG. 9, the CN 3 sends theobtained SMS data to an entity related to SMS (e.g., SMS-GMSC,SMS-IWMSC, SMS router).

In some implementations, when the UE 1 initiates data transmission inaccordance with the first communication architecture (Step 903), it maydelete or release the previous RRC connection context retained for thesuspension operation for the second communication architecture type. Thememory area in which this RRC connection context has been stored may bereused to store an RRC connection context for the communication inaccordance with the first communication architecture type. In otherwords, the previous RRC connection context for the suspension operationfor the second communication architecture type may be overwritten (orupdated) by a new RRC connection context for the communication inaccordance with the first communication architecture type. Suchconfiguration and operation can reduce the memory capacity that the UE 1should have, which is particularly effective for NB-CIoT that requirescost optimization and low power consumption.

When the previous RRC connection context retained in the UE 1 for thesuspension operation for the second communication architecture type isdeleted or released, the UE 1 may inform the RAN 2, or the CN 3, or bothabout this deletion or release. Specifically, in the control procedure(Steps 904 to 907) for initiating the communication in accordance withthe first communication architecture type, the UE 1 may transmit anindication indicating discarding of the RRC connection context to thenetwork (i.e., the RAN 2, or the CN 3, or both). For example, the UE 1may include the indication in an RRC message (e.g., RRC ConnectionRequest, RRC Connection Setup Complete), or a NAS message, or both.

In response to receiving this indication from the UE 1, the RAN 2 mayrecognize that the information (e.g., RRC connection context, S1APassociation, S1-U bearer context) retained in the RAN 2 for thesuspension operation is allowed to be discarded or released. Likewise,in response to receiving the indication from the UE 1, the CN 3 mayrecognize that the information (e.g., S1AP association, S1-U bearercontext) retained in the CN 3 for the suspension operation is allowed tobe discarded or released. Such configuration and operation can preventthe suspended states of the UE 1 and the network from being inconsistentwith each other.

Alternatively, when the UE 1 initiates data transmission in accordancewith the first communication architecture (Step 903), the UE 1 maymaintain the previous RRC connection context retained for the suspensionoperation for the second communication architecture type.

FIG. 10 is a sequence diagram showing another example of thecommunication procedure according to this embodiment. FIG. 10 shows anexample of Mobile Terminated (MT) small data transmission. Step 1001 issimilar to Step 901 in FIG. 9. In Step 1002, the CN 3 (e.g., MME, C-SGN)receives a paging message indicating the arrival of Mobile-TerminatedSMS data addressed to the UE 1. The CN 3 may receive SMS data in Step1002. In this case, Step 1008 described below may be omitted.

In Step 1003, the CN 3 sends a paging message to the RAN 2.Specifically, the CN 3 sends a paging message to respective eNBs (orCIoT-BSs) associated with one or more cells belonging to one or moretracking areas of the UE 1. In Step 1004, the UE 1 is paged by the RAN2.

In Step 1005, in response to receiving the paging related to the firstcommunication architecture type while the UE 1 is executing thesuspension operation for the second communication architecture type, theUE 1 switches from the second communication architecture type to thefirst communication architecture type and initiates communication inaccordance with the first communication architecture type (i.e., datatransmission over NAS). Here, the paging related to the firstcommunication architecture type may include, for example, informationexplicitly or implicitly indicating that the data transmission inaccordance with the first communication architecture type is to becarried out. The explicit information may be information indicating oneof the first communication architecture type and the secondcommunication architecture type, or information indicating the firstcommunication architecture type. The implicit information may be abearer ID. Alternatively, the UE 1 may be configured to always respondusing the first communication architecture type whenever it is paged.

The procedure for the data transmission in accordance with the firstcommunication architecture type may be similar to the Mobile Terminated(MT) small data transmission procedure for the solution 2 (i.e., DoNAS)disclosed in Non Patent Literature 1. That is, in Step 1006, the UE 1establishes an RRC connection and transmits a NAS message (i.e., ServiceRequest) to the CN 3 using an RRC Connection Setup Complete message(Step 1007). The CN 3 receives SMS data (Step 1008), encapsulates thisSMS data in a NAS message, and sends this NAS message to the RAN 2 (Step1009). The RAN 2 receives the NAS message carrying the SMS data from theCN 3 and transmits an RRC message (e.g., DL Information Transfer)containing this NAS message to the UE 1 (Step 1010). As alreadydescribed, at the present time, it is assumed that neither the solution2 nor the solution 18 will use SRB 2. Thus, the RRC message of Step 1010may be transmitted using SRB 1 on a Dedicated Control Channel (DCCH).

Similarly to the example of FIG. 9, in the example of FIG. 10, when theprevious RRC connection context retained in the UE 1 for the suspensionoperation for the second communication architecture type is deleted orreleased, the UE 1 may inform the RAN 2, or the CN 3, or both about thisdeletion or release. In response to receiving this indication from theUE 1, the RAN 2 may recognize that the information (e.g., RRC connectioncontext, S1AP association, S1-U bearer context) retained in the RAN 2for the suspension operation is allowed to be discarded or released.Likewise, in response to receiving this indication from the UE 1, the CN3 may recognize that the information (e.g., S1AP association, S1-Ubearer context) retained in the CN 3 for the suspension operation isallowed to be discarded or released. Such configuration and operationcan prevent the suspended states of the UE 1 and the network from beinginconsistent with each other.

Eighth Embodiment

In this embodiment, a configuration example of a radio communicationnetwork is similar to that in FIG. 2. The UE 1 according to thisembodiment may be a CIoT device (e.g., NB-IoT, LTE eMTC), or may beanother UE in LTE, LTE-Advanced, or modified versions thereof.

As already described, at the present time, it is assumed that thesolution 2 (i.e., DoNAS, Control Plane CIoT EPS optimisation) does notuse the AS security and the PDCP. In some implementations, DoNAScommunication that does not use the PDCP may be performed simply withouttraversing the PDCP layer. Alternatively, a new operation mode (e.g.,PDCP Transparent Mode (PDCP-TM)) of the PDCP layer may be defined forDoNAS communication that does not use the PDCP. In such new operationmode (PDCP-TM), the PDCP layer does not provide some PDCP-layerfunctions including the AS security function (e.g., integrity protectionfor SRB, ciphering).

Some of the above-described embodiments have shown examples in which theUE 1 executes the RRC Connection Resume procedure to initiate datatransmission in accordance with the first communication architecturetype while the UE 1 is executing the suspension operation for the secondcommunication architecture type (e.g., FIGS. 4 and 5). Since the secondcommunication architecture type (i.e., AS context caching, User PlaneCIoT EPS optimisation) uses the AS security, the UE 1 and RAN 2 performsecurity activation (or confirmation) at one of the stages of the RRCConnection Resume procedure. Thus, when the AS security has already beenactivated in the RRC Connection Resume procedure, the UE 1 and RAN 2 mayapply the AS security (e.g., integrity protection for SRB, ciphering) tothe communication of the first communication architecture type (i.e.,DoNAS, Control Plane CIoT EPS optimisation).

Ninth Embodiment

3GPP plans to start working on the standardization for 5G, i.e., 3GPPRelease 14, in 2016 towards the introduction of 5G in 2020. 5G isexpected to be realized by continuous enhancement/evolution of LTE andLTE-Advanced and an innovative development by an introduction of a new5G air-interface (i.e., a new Radio Access Technology (RAT)). The newRAT (i.e., New 5G RAT) supports, for example, frequency bands higherthan the frequency bands (e.g., 6 GHz or lower) supported by theLTE/LTE-Advanced and its enhancement/evolution. For example, the new RATsupports centimeter-wave bands (10 GHz or higher) and millimeter-wavebands (30 GHz or higher).

Higher frequency can provide higher-rate communication. However, becauseof its frequency properties, coverage of the higher frequency is morelocal. Therefore, high frequencies are used to boost capacity and datarates in specific areas, while wide-area coverage is provided by lowercurrent frequencies. That is, in order to ensure the stability of New 5GRAT communication in high frequency bands, tight integration orinterworking between low and high frequencies (i.e., tight integrationor interworking between LTE/LTE-Advanced and New 5G RAT) is required. A5G supporting radio terminal (i.e., 5G User Equipment (UE)) is connectedto both of a low frequency band cell and a high frequency band cell(i.e., a LTE/LTE-Advanced cell and a new 5G cell) by using CarrierAggregation (CA) or Dual Connectivity (DC), or a modified techniquethereof.

The term “LTE” used in this specification includes enhancements of LTEand LTE-Advanced for 5G to provide tight interworking with the New 5GRAT, unless otherwise indicated. Such enhancements of LTE andLTE-Advanced are also referred to as LTE-Advanced Pro, LTE+, or enhancedLTE (eLTE). Further, the term “5G” or “New 5G” in this specification isused, for the sake of convenience, to indicate an air-interface (RAT)that is newly introduced for the fifth generation (5G) mobilecommunication systems, and nodes, cells, protocol layers, etc. relatedto this air-interface. The names of the newly introduced air interface(RAT), and nodes, cells, and protocol layers related thereto will bedetermined in the future as the standardization work progresses. Forexample, the LTE RAT may be referred to as Primary RAT (P-RAT or pRAT)or Master RAT. Meanwhile, the New 5G RAT may be referred to as SecondaryRAT (S-RAT or sRAT).

The first to eighth embodiments described above may be applied to a 5Gradio communication network that provides tight interworking between theLTE RAT and the New 5G RAT. In some implementations, the UE 1, RAN 2,and CN 3 may perform any one of the attach procedures described in thefirst to eighth embodiments in the LTE RAT then perform datatransmission in the New 5G RAT according to a communication architecturetype determined (or selected) in the attach procedure.

For example, when the first communication architecture type is used forthe UE 1, the UE 1 may transmit data using a UL Information Transfermessage in the 5G cell, instead of using an RRC Connection SetupComplete message in the LTE cell, and receive data using a DLInformation Transfer message in the 5G cell. For example, when thesecond communication architecture type is used for the UE 1, the UE 1,the RAN 2, and the CN 3 may perform suspension and resumption of an RRCconnection in the 5G cell. In this process, the UE 1 and the RAN 2 maybe connected to both a core network node for communication in the LTEcell and a core network node different from that for the communicationin the LTE cell.

Lastly, configuration examples of the UE 1, the nodes in the RAN 2(e.g., CIoT BS, eNB), and the nodes in the CN 3 (e.g., C-SGN, MME)according to the above-described plurality of embodiments will bedescribed. FIG. 11 is a block diagram showing a configuration example ofthe UE 1. A Radio Frequency (RF) transceiver 1101 performs analog RFsignal processing to communicate with the RAN 2. The analog RF signalprocessing performed by the RF transceiver 1101 includes frequencyup-conversion, frequency down-conversion, and amplification. The RFtransceiver 1101 is coupled to an antenna 1102 and a baseband processor1103. That is, the RF transceiver 1101 receives modulation symbol data(or OFDM symbol data) from the baseband processor 1103, generates atransmission RF signal, and supplies the transmission RF signal to theantenna 1102. Moreover, the RF transceiver 1101 generates a basebandreception signal based on a reception RF signal received by the antenna1102, and supplies the baseband reception signal to the basebandprocessor 1103.

The baseband processor 1103 performs digital baseband signal processing(data-plane processing) and control-plane processing for radiocommunication. The digital baseband signal processing includes, forexample, (a) data compression/decompression, (b) datasegmentation/concatenation, (c) composition/decomposition of atransmission format (i.e., transmission frame), (d) channelcoding/decoding, (e) modulation (i.e., symbol mapping)/demodulation, and(f) generation of OFDM symbol data (i.e., baseband OFDM signal) byInverse Fast Fourier Transform (IFFT). Meanwhile, the control-planeprocessing includes communication management of the layer 1 (e.g.,transmission power control), layer 2 (e.g., radio resource managementand hybrid automatic repeat request (HARQ) processing), and layer 3(e.g., signaling regarding attach, mobility, and call management).

In the case of LTE and LTE-Advanced, for example, the digital basebandsignal processing by the baseband processor 1103 may include signalprocessing of the Packet Data Convergence Protocol (PDCP) layer, RadioLink Control (RLC) layer, Medium Access Control (MAC) layer, andPhysical (PHY) layer. Further, the control-plane processing by thebaseband processor 1103 may include the processing of the Non-AccessStratum (NAS) protocol, the RRC protocol, and the MAC Control Elements(MAC CEs).

The baseband processor 1103 may include a modem processor (e.g., DigitalSignal Processor (DSP)) that performs the digital baseband signalprocessing and a protocol stack processor (e.g., Central Processing Unit(CPU) or Micro Processing Unit (MPU)) that performs the control-planeprocessing. In this case, the protocol stack processor, which performsthe control-plane processing, may be integrated with an applicationprocessor 1104 described in the following.

The application processor 1104 may also be referred to as a CPU, an MPU,a microprocessor, or a processor core. The application processor 1104may include a plurality of processors (processor cores). The applicationprocessor 1104 loads a system software program (Operating System (OS))and various application programs (e.g., a voice call application, a WEBbrowser, a mailer, a camera operation application, a music playbackapplication) from a memory 1106 or from another memory (not shown) andexecutes these programs, thereby providing various functions of the UE1.

In some implementations, as represented by the dashed line (1105) inFIG. 11, the baseband processor 1103 and the application processor 1104may be integrated on a single chip. In other words, the basebandprocessor 1103 and the application processor 1104 may be implemented ina single System on Chip (SoC) device 1105. A SoC device may be referredto as a system Large Scale Integration (LSI) or a chipset.

The memory 1106 is a volatile memory or a non-volatile memory or acombination thereof. The memory 1106 is a volatile memory or anon-volatile memory or a combination thereof. The volatile memory is,for example, Static Random Access Memory (SRAM), Dynamic RAM (DRAM) or acombination thereof. The non-volatile memory may be a Mask Read OnlyMemory (MROM), an Electrically Erasable Programmable ROM (EEPROM), aflash memory, a hard disk drive, or any combination thereof. The memory1106 may include an internal memory device integrated within thebaseband processor 1103, the application processor 1104, or the SoC1105. Further, the memory 1106 may include a memory in a UniversalIntegrated Circuit Card (UICC).

The memory 1106 may store one or more software modules (computerprograms) 1107 including instructions and data for processing by the UE1 described in the above embodiments. In some implementations, thebaseband processor 1103 or the application processor 1104 may be loadthese one or more software modules 1107 from the memory 1106 and executethe loaded software modules, thereby performing the processing of the UE1 described in the above embodiments.

FIG. 12 is a block diagram showing a configuration example of a node(e.g., CIoT BS, eNB) in the RAN 2 according to the above embodiments.Referring to FIG. 12, the node includes an RF transceiver 1201, anetwork interface 1203, a processor 1204, and a memory 1205. The RFtransceiver 1201 performs analog RF signal processing to communicatewith a radio terminal 1. The RF transceiver 1201 may include a pluralityof transceivers.

The RF transceiver 1201 is coupled to an antenna 1202 and a processor1204. The RF transceiver 1201 receives modulation symbol data (or OFDMsymbol data) from the processor 1204, generates a transmission RFsignal, and supplies the transmission RF signal to the antenna 1202.Moreover, the RF transceiver 1201 generates a baseband reception signalbased on a reception RF signal received by the antenna 1202, andsupplies the baseband reception signal to the processor 1204.

The network interface 1203 is used to communicate with network nodes(e.g., MME, C-SGN, S-GW). The network interface 1203 may include, forexample, a network interface card (NIC) conforming to the IEEE 802.3series.

The processor 1204 performs digital baseband signal processing(data-plane processing) and control-plane processing for radiocommunication. In the case of LTE and LTE-Advanced, for example, thedigital baseband signal processing performed by the processor 1204 mayinclude signal processing of the PDCP layer, RLC layer, MAC layer, andPHY layer. Further, the control-plane processing performed by theprocessor 1204 may include the processing of the S1 protocol, RRCprotocol, and MAC CEs.

The processor 1204 may include a plurality of processors. The basebandprocessor 1204 may include a modem processor (e.g., DSP) that performsthe digital baseband signal processing and a protocol stack processor(e.g., CPU or MPU) that performs the control-plane processing.

The memory 1205 is composed of a combination of a volatile memory and anon-volatile memory. The volatile memory is, for example, an SRAM, aDRAM, or a combination thereof. The non-volatile memory may be a MROM, aPROM, a flash memory, a hard disk drive, or a combination thereof. Thememory 1205 may include a storage disposed separately from the processor1204. In this case, the processor 1204 may access the memory 1205 viathe network interface 1203 or an I/O interface not shown.

The memory 1205 may store one or more software modules (computerprograms) 1206 including instructions and data for processing by thenode in the RAN 2 (e.g., CIoT BS, eNB) described in the aboveembodiments. In some implementations, the processor 1204 may load theseone or more software modules from the memory 1205 and execute the loadedsoftware modules, thereby performing the processing of the node in theRAN 2 described in the above embodiments.

FIG. 13 is a block diagram showing a configuration example of a node(e.g., C-SGN, MME) in the CN 3 according to the above embodiments.Referring to FIG. 13, the node includes a network interface 1301, aprocessor 1302, and a memory 1303. The network interface 1301 is used tocommunicate with network nodes (e.g., C-SGN, MME, HSS, S-GW, P-GW, CIoTBS, eNB). The network interface 1301 may include, for example, a networkinterface card (NIC) conforming to the IEEE 802.3 series.

The processor 1302 loads one or more software modules (computerprograms) from the memory 1303 and executes the loaded software modules,thereby performing the processing of the node in the CN 3 (e.g., C-SGN,MME) described in the above embodiments. The processor 1302 may be, forexample, a microprocessor, MPU, or CPU. The processor 1302 may include aplurality of processors.

The memory 1303 is composed of a combination of a volatile memory and anon-volatile memory. The memory 1303 may include a storage disposedseparately from the processor 1302. In this case, the processor 1302 mayaccess the memory 1303 via an I/O interface (not shown).

As described with reference to FIGS. 11 and 13, each of the processorsincluded in the UE 1, the node in the RAN 2, and the node in the CN 3according to the above-described embodiments executes one or moreprograms including instructions to cause a computer to perform thealgorithm described with reference to the drawings. These programs canbe stored and provided to a computer using any type of non-transitorycomputer readable media. Non-transitory computer readable media includeany type of tangible storage media. Examples of non-transitory computerreadable media include magnetic storage media (such as floppy disks,magnetic tapes, hard disk drives, etc.), optical magnetic storage media(e.g. magneto-optical disks), Compact Disc Read Only Memory (CD-ROM),CD-R, CD-R/W, semiconductor memories (such as Mask ROM, Programmable ROM(PROM), Erasable PROM (EPROM), flash ROM, Random Access Memory (RAM)).These programs may be provided to a computer using any type oftransitory computer readable media. Examples of transitory computerreadable media include electric signals, optical signals, andelectromagnetic waves. Transitory computer readable media can be used toprovide programs to a computer via a wired communication line (e.g.,electric wires, and optical fibers) or a wireless communication line.

Other Embodiments

Each of the above embodiments may be used individually, or two or moreof the embodiments may be appropriately combined with one another.

In the above embodiments, when the UE 1 changes the serving cell fromthe cell in which the RRC connection has been suspended to another cell(e.g., cell reselection, attach after detach), it may be preferable thatthe UE 1 can know whether the functions described in the aboveembodiment are available in the serving cell after the change of cell.Thus, the RAN 2 may broadcast an information element indicating whetherthe functions are supported in the serving cell. For example, the RAN 2(e.g., eNB, CIoT-BS) may broadcast this information element inrespective cells in the RAN 2. The information element may indicatewhether the cell in which this information element is broadcastedsupports the functions. Furthermore, the information element mayindicate whether an adjacent cell supports the functions.

The RAN 2 described in the above embodiments may be a Cloud Radio AccessNetwork (C-RAN). The C-RAN is also referred to as a Centralized RAN.Specifically, the processes and operations performed by the RAN 2, orthe CIoT BS or the eNB in the RAN 2, described in the above embodimentsmay be provided by one or a combination of a Digital Unit (DU) and aRadio Unit (RU) included in the C-RAN architecture. The DU is alsoreferred to as a Baseband Unit (BBU). The RU is also referred to as aRemote Radio Head (RRH) or Remote Radio Equipment (RRE). That is, theprocesses and operations performed by the RAN 2, the CIoT BS, or the eNBdescribed in the above embodiments may be provided by any one or moreradio stations (i.e., RAN nodes).

The above-described embodiments are merely examples of applications ofthe technical ideas obtained by the inventors. These technical ideas arenot limited to the above-described embodiments, and various changes andmodifications may be thereto.

For example, the whole or part of the embodiments disclosed above can bedescribed as, but not limited to, the following supplementary notes.

(Supplementary Note A1)

A radio terminal comprising:

a memory; and

at least one processor coupled to the memory, wherein

the at least one processor is configured to support a plurality ofcommunication architecture types,

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the at least one processor is further configured to, in response to anoccurrence of a request for specific data transmission when the radioterminal has already been configured by a network to use the secondcommunication architecture type, transmit data using the firstcommunication architecture type.

(Supplementary Note A2)

The radio terminal according to Supplementary note A1, wherein thespecific data transmission includes non-Internet Protocol (non-IP) datatransmission.

(Supplementary Note A3)

The radio terminal according to Supplementary note A1 or A2, wherein thespecific data transmission includes Short Message Service (SMS) datatransmission.

(Supplementary Note A4)

The radio terminal according to any one of Supplementary notes A1 to A3,wherein the specific data transmission includes data transmission ofonly one packet.

(Supplementary Note A5)

The radio terminal according to any one of Supplementary notes A1 to A4,wherein the specific data transmission includes data transmissionrelated to a predetermined service.

(Supplementary Note A6)

The radio terminal according to any one of Supplementary notes A1 to A5,wherein

the radio terminal is adapted to be configured by the network to useboth the first and second communication architecture types, and

the at least one processor is configured to determine which of the firstand second communication architecture types is to be used, depending onwhether requested communication is the specific data transmission.

(Supplementary Note A7)

The radio terminal according to any one of Supplementary notes A1 to A5,wherein

the radio terminal is adapted to be configured by the network to useeither of the first and second communication architecture types and notto simultaneously use both the first and second communicationarchitecture types, and

the at least one processor is configured to switch from the secondcommunication architecture type to the first communication architecturetype in response to the occurrence of the request for the specific datatransmission.

(Supplementary Note A8)

A method in a radio terminal, the method comprising:

being configured by a network with at least one of a plurality ofcommunication architecture types, wherein

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the method further comprises, in response to an occurrence of a requestfor specific data transmission when the radio terminal has already beenconfigured by the network to use the second communication architecturetype, transmitting data using the first communication architecture type.

(Supplementary Note B1)

A radio terminal comprising:

a memory; and

at least one processor coupled to the memory, wherein

the at least one processor is configured to support a plurality ofcommunication architecture types,

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the at least one processor is further configured to, in response to anoccurrence of a request for data transmission in accordance with thefirst communication architecture type while the radio terminal isexecuting the suspension for the second communication architecture type,initiate communication in accordance with the first communicationarchitecture type while retaining the context.

(Supplementary Note B2)

The radio terminal according to Supplementary note B 1, wherein

the at least one processor is configured to transmit a Non-AccessStratum (NAS) message containing data of the first communicationarchitecture type using an RRC message that is used for the resumptionof the RRC connection, and

the RRC message includes an indication indicating data transmission overa Non-Access Stratum (NAS).

(Supplementary Note B3)

The radio terminal according to Supplementary note B1 or B2, wherein

the at least one processor is configured to transmit the Non-AccessStratum (NAS) message containing the data of the first communicationarchitecture type using an RRC message that is used for the resumptionof the RRC connection, and

the NAS message includes an indication indicating the data transmissionover the Non-Access Stratum (NAS).

(Supplementary Note B4)

A method in a radio terminal, the method comprising:

being configured by a network with at least one of a plurality ofcommunication architecture types, wherein

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the method further comprises, in response to an occurrence of a requestfor data transmission in accordance with the first communicationarchitecture type while the radio terminal is executing the suspensionfor the second communication architecture type, initiating communicationin accordance with the first communication architecture type whileretaining the context.

(Supplementary Note C1)

A radio terminal comprising:

a memory; and

at least one processor coupled to the memory, wherein

the at least one processor is configured to support a plurality ofcommunication architecture types,

the plurality of communication architecture types include (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the at least one processor is further configured to, in response to anoccurrence of a request for data transmission in accordance with thefirst communication architecture type while the radio terminal isexecuting the suspension for the second communication architecture type,discard or release the context and initiate communication in accordancewith the first communication architecture type.

(Supplementary Note C2)

The radio terminal according to Supplementary note C1, wherein the atleast one processor is configured to transmit an indication indicatingdiscarding of the context to a network during a control procedure forinitiating the communication in accordance with the first communicationarchitecture type.

(Supplementary Note C3)

The radio terminal according to Supplementary note C2, wherein the atleast one processor is configured to include the indication in either orboth of an RRC message and a Non-Access Stratum (NAS) message to betransmitted in the control procedure.

(Supplementary Note C4)

A radio station in a radio access network, the radio station comprising:

a memory; and

at least one processor coupled to the memory, wherein

the at least one processor is configured to support a plurality ofcommunication architecture types,

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radiostation a first context regarding a previous RRC connection while aradio terminal is in an RRC idle state,

the resumption of the RRC connection includes reusing the retained firstcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the at least one processor is further configured to recognize that thefirst context is allowed to be discarded or released, in response toreceiving an RRC message for data transmission in accordance with thefirst communication architecture type while the radio station isexecuting the suspension for the radio terminal.

(Supplementary Note C5)

The radio station according to Supplementary note C4, wherein

the RRC message includes an indication indicating discarding orreleasing of a second context retained in the radio terminal for thesuspension, and

the at least one processor is configured to, in response to receivingthe indication, recognize that the first context is allowed to bediscarded or released.

(Supplementary Note C6)

A network apparatus in a core network comprising:

a memory; and

at least one processor coupled to the memory, wherein

the at least one processor is configured to support a plurality ofcommunication architecture types,

the plurality of communication architecture type include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining, in the networkapparatus, a signaling association for a radio terminal between thenetwork apparatus and a radio station and a bearer context for the radioterminal, while the radio terminal is in an RRC idle state,

the resumption of the RRC connection includes reusing or restoring theretained signaling association and the bearer context along with a setupof a subsequent RRC connection in order for the radio terminal totransition from the RRC idle state to an RRC connected state, and

the at least one processor is further configured to recognize that theretained signaling association and the retained bearer context areallowed to be discarded or released, in response to receiving, from theradio terminal or the radio station, a control message for datatransmission in accordance with the first communication architecturetype while the network apparatus is executing the suspension for theradio terminal.

(Supplementary Note C7)

The radio station according to Supplementary note C6, wherein

the control message includes an indication indicating discarding orreleasing of the second context regarding the RRC connection retained inthe radio terminal for the suspension, and

the at least one processor is configured to, in response to receivingthe indication, recognize that the signaling association and the bearercontext are allowed to be discarded or released.

(Supplementary Note C8)

The network apparatus according to Supplementary note C6 or C7 whereinthe control message includes a Non-Access Stratum (NAS) message, or anS1 Application Protocol (S1AP) message, or both.

(Supplementary Note C9)

A method in a radio terminal, the method comprising:

being configured by a network with at least one of a plurality ofcommunication architecture types, wherein

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the method further comprises, in response to an occurrence of a requestfor data transmission in accordance with the first communicationarchitecture type while the radio terminal is executing the suspensionfor the second communication architecture type, discarding or releasingthe context and initiating communication in accordance with the firstcommunication architecture type.

(Supplementary Note C10)

A method in a radio station in a radio access network, the methodcomprising:

supporting a plurality of communication architecture types, wherein

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radiostation a first context regarding a previous RRC connection while aradio terminal is in an RRC idle state,

the resumption of the RRC connection includes reusing the retained firstcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state, and

the method further comprises recognizing that the first context isallowed to be discarded or released, in response to receiving an RRCmessage for data transmission in accordance with the first communicationarchitecture type while the radio station is executing the suspensionfor the radio terminal.

(Supplementary Note C11)

A method in a network apparatus in a core network, the methodcomprising:

supporting a plurality of communication architecture types, wherein

the plurality of communication architecture type include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining, in the networkapparatus, a signaling association for a radio terminal between thenetwork apparatus and a radio station and a bearer context for the radioterminal, while the radio terminal is in an RRC idle state,

the resumption of the RRC connection includes reusing or restoring theretained signaling association and the bearer context along with a setupof a subsequent RRC connection in order for the radio terminal totransition from the RRC idle state to an RRC connected state, and

the method further comprises recognizing that the retained signalingassociation and the retained bearer context are allowed to be discardedor released, in response to receiving, from the radio terminal or theradio station, a control message for data transmission in accordancewith the first communication architecture type while the networkapparatus is executing the suspension for the radio terminal.

(Supplementary Note D1)

A radio terminal comprising:

a memory; and

at least one processor coupled to the memory, wherein

the at least one processor is configured to support a plurality ofcommunication architecture types,

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state,

the at least one processor is further configured to, in response to anoccurrence of a request for specific data transmission in accordancewith the first communication architecture type while the radio terminalis executing the suspension for the second communication architecturetype, transmit an RRC connection resume message used for the resumptionof the RRC connection, and

the RRC connection resume message indicates an establishment causeassociated with data transmission over a Non-Access Stratum (NAS).

(Supplementary Note D2)

The radio terminal according to Supplementary note D1, wherein

the specific data transmission is non-Internet Protocol (non-IP) datatransmission or Short Message Service (SMS) transmission,

the at least one processor is configured to operate as an NAS layer thatprovides mobility management and session management and as an AccessStratum (AS) layer that provides radio resource control, and

the NAS layer is configured to, in response to the occurrence of therequest for the specific data transmission while the radio terminal isexecuting the suspension for the second communication architecture type,generate a NAS message carrying data and provided a request for RRCconnection establishment to the AS layer, the request for RRC connectionestablishment containing the establishment cause associated with thedata transmission over the NAS and a call type associated with thespecific transmission.

(Supplementary Note D3)

A radio station in a radio access network comprising:

a memory; and

at least one processor coupled to the memory, wherein

the at least one processor is configured to support a plurality ofcommunication architecture types,

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radiostation a context regarding a previous RRC connection while a radioterminal is in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state,

the at least one processor is further configured to receive an RRCconnection resume message used for the resumption of the RRC connectionwhile the radio station is executing the suspension for the radioterminal, and

the at least one processor is further configured to, in response to theRRC connection resume message indicating an establishment causeassociated with data transmission over a Non-Access Stratum (NAS),recognize that communication is in accordance with the firstcommunication architecture type.

(Supplementary Note D4)

The radio station according to Supplementary note D3, wherein

the suspension of the RRC connection further includes retaining in theradio station and a core network a bearer context regarding a bearer forthe radio terminal between the radio station and the core network whilethe radio terminal is in the RRC idle state,

the resumption of the RRC connection further includes restoring orreusing the bearer based on the bearer context along with the setup ofthe subsequent RRC connection, and

the at least one processor is configured to prevent itself fromrequesting the core network to restore or reuse the bearer, when the RRCconnection resume message indicates the establishment cause associatedwith the data transmission over the Non-Access Stratum (NAS).

(Supplementary Note D5)

A method in a radio terminal, the method comprising:

being configured by a network with at least one of a plurality ofcommunication architecture types, wherein

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state,

the method further comprises, in response to an occurrence of a requestfor specific data transmission in accordance with the firstcommunication architecture type while the radio terminal is executingthe suspension for the second communication architecture type,transmitting an RRC connection resume message used for the resumption ofthe RRC connection, and

the RRC connection resume message indicates an establishment causeassociated with data transmission over a Non-Access Stratum (NAS).

(Supplementary Note D6)

A method in a radio station in a radio access network, the methodcomprising:

supporting a plurality of communication architecture types, wherein

the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,

the suspension of the RRC connection includes retaining in the radiostation a context regarding a previous RRC connection while a radioterminal is in an RRC idle state,

the resumption of the RRC connection includes reusing the retainedcontext at the time of a setup of a subsequent RRC connection in orderfor the radio terminal to transition from the RRC idle state to an RRCconnected state,

the at least one processor is further configured to receive an RRCconnection resume message used for the resumption of the RRC connectionwhile the radio station is executing the suspension for the radioterminal, and

the method further comprises, in response to the RRC connection resumemessage indicating an establishment cause associated with datatransmission over a Non-Access Stratum (NAS), recognizing thatcommunication is in accordance with the first communication architecturetype.

The present application is based upon and claims the benefit of priorityfrom Japanese Patent Application No. 2016-020291, filed on Feb. 4, 2016,the entire contents of which are hereby incorporated by reference.

REFERENCE SIGNS LIST

-   1 User Equipment (UE)-   2 Radio Access Network (RAN)-   3 Core Network (CN)-   4 APPLICATION SERVER-   6 Serving Gateway (S-GW)/Packet Data Network Gateway (P-GW)-   1103 BASEBAND PROCESSOR-   1104 APPLICATION PROCESSOR-   1106 MEMORY-   1204 PROCESSOR-   1205 MEMORY-   1302 PROCESSOR-   1303 MEMORY

1. A radio terminal comprising: a memory; and at least one processorcoupled to the memory, wherein the at least one processor is configuredto support a plurality of communication architecture types, theplurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,the suspension of the RRC connection includes retaining in the radioterminal a context of a previous RRC connection while the radio terminalis in an RRC idle state, the resumption of the RRC connection includesreusing the retained context at the time of a setup of a subsequent RRCconnection in order for the radio terminal to transition from the RRCidle state to an RRC connected state, and the at least one processor isfurther configured to, in response to an occurrence of a request forspecific data transmission when the radio terminal has already beenconfigured by a network to use the second communication architecturetype, transmit data using the first communication architecture type. 2.The radio terminal according to claim 1, wherein the specific datatransmission includes non-Internet Protocol (non-IP) data transmission.3. The radio terminal according to claim 1, wherein the specific datatransmission includes Short Message Service (SMS) data transmission. 4.The radio terminal according to claim 1, wherein the specific datatransmission includes data transmission of only one packet.
 5. The radioterminal according to claim 1, wherein the specific data transmissionincludes data transmission related to a predetermined service.
 6. Theradio terminal according to claim 1, wherein the radio terminal isadapted to be configured by the network to use both the first and secondcommunication architecture types, and the at least one processor isconfigured to determine which of the first and second communicationarchitecture types is to be used, depending on whether requestedcommunication is the specific data transmission.
 7. The radio terminalaccording to claim 1, wherein the radio terminal is adapted to beconfigured by the network to use either of the first and secondcommunication architecture types and not to simultaneously use both thefirst and second communication architecture types, and the at least oneprocessor is configured to switch from the second communicationarchitecture type to the first communication architecture type inresponse to the occurrence of the request for the specific datatransmission.
 8. The radio terminal according to claim 1, wherein the atleast one processor is further configured to, in response to anoccurrence of a request for data transmission in accordance with thefirst communication architecture type while the radio terminal isexecuting the suspension for the second communication architecture type,initiate communication in accordance with the first communicationarchitecture type while retaining the context.
 9. The radio terminalaccording to claim 8, wherein the at least one processor is configuredto transmit a Non-Access Stratum (NAS) message containing data of thefirst communication architecture type using an RRC message that is usedfor the resumption of the RRC connection, and the RRC message includesan indication indicating data transmission over a Non-Access Stratum(NAS).
 10. The radio terminal according to claim 8, wherein the at leastone processor is configured to transmit the Non-Access Stratum (NAS)message containing the data of the first communication architecture typeusing an RRC message that is used for the resumption of the RRCconnection, and the NAS message includes an indication indicating thedata transmission over a Non-Access Stratum (NAS).
 11. The radioterminal according to claim 1, wherein the at least one processor isfurther configured to, in response to an occurrence of a request fordata transmission in accordance with the first communicationarchitecture type while the radio terminal is executing the suspensionfor the second communication architecture type, discard or release thecontext and initiate communication in accordance with the firstcommunication architecture type.
 12. The radio terminal according toclaim 11, wherein the at least one processor is configured to transmitan indication indicating discarding of the context to the network duringa control procedure for initiating the communication in accordance withthe first communication architecture type.
 13. The radio terminalaccording to claim 12, wherein the at least one processor is configuredto include the indication in either or both of an RRC message and aNon-Access Stratum (NAS) message to be transmitted in the controlprocedure.
 14. The radio terminal according to claim 1, wherein the atleast one processor is further configured to, in response to anoccurrence of a request for specific data transmission in accordancewith the first communication architecture type while the radio terminalis executing the suspension for the second communication architecturetype, transmit an RRC connection resume message used for the resumptionof the RRC connection, and the RRC connection resume message indicatesan establishment cause associated with data transmission over aNon-Access Stratum (NAS).
 15. The radio terminal according to claim 14,wherein the specific data transmission is non-Internet Protocol (non-IP)data transmission or Short Message Service (SMS) transmission, the atleast one processor is configured to operate as an NAS layer thatprovides mobility management and session management and as an AccessStratum (AS) layer that provides radio resource control, and the NASlayer is configured to, in response to the occurrence of the request forthe specific data transmission while the radio terminal is executing thesuspension for the second communication architecture type, generate aNAS message carrying data and provides a request for RRC connectionestablishment to the AS layer, the request for RRC connectionestablishment containing the establishment cause associated with thedata transmission over the NAS and a call type associated with thespecific transmission.
 16. A radio station used in a radio accessnetwork, the radio station comprising: a memory; and at least oneprocessor coupled to the memory, wherein the at least one processor isconfigured to support a plurality of communication architecture types,the plurality of communication architecture types include: (a) a firstcommunication architecture type in which a data packet is transmittedvia a control plane; and (b) a second communication architecture type inwhich a data packet is transmitted via a user plane and that involvessuspension and resumption of a Radio Resource Control (RRC) connection,the suspension of the RRC connection includes retaining in the radiostation a context regarding a previous RRC connection while a radioterminal is in an RRC idle state, the resumption of the RRC connectionincludes reusing the retained context at the time of a setup of asubsequent RRC connection in order for the radio terminal to transitionfrom the RRC idle state to an RRC connected state, the at least oneprocessor is further configured to receive an RRC connection resumemessage used for the resumption of the RRC connection while the radiostation is executing the suspension for the radio terminal, and the atleast one processor is further configured to, in response to the RRCconnection resume message indicating an establishment cause associatedwith data transmission over a Non-Access Stratum (NAS), recognize thatcommunication is in accordance with the first communication architecturetype.
 17. The radio station according to claim 16, wherein thesuspension of the RRC connection further includes retaining in the radiostation and a core network a bearer context regarding a bearer for theradio terminal between the radio station and the core network while theradio terminal is in the RRC idle state, the resumption of the RRCconnection further includes restoring or reusing the bearer based on thebearer context along with the setup of the subsequent RRC connection,and the at least one processor is configured to prevent itself fromrequesting the core network to restore or reuse the bearer, when the RRCconnection resume message indicates the establishment cause associatedwith the data transmission over the Non-Access Stratum (NAS).
 18. Amethod in a radio terminal, the method comprising: being configured by anetwork with at least one of a plurality of communication architecturetypes, wherein the plurality of communication architecture typesinclude: (a) a first communication architecture type in which a datapacket is transmitted via a control plane; and (b) a secondcommunication architecture type in which a data packet is transmittedvia a user plane and that involves suspension and resumption of a RadioResource Control (RRC) connection, the suspension of the RRC connectionincludes retaining in the radio terminal a context of a previous RRCconnection while the radio terminal is in an RRC idle state, theresumption of the RRC connection includes reusing the retained contextat the time of a setup of a subsequent RRC connection in order for theradio terminal to transition from the RRC idle state to an RRC connectedstate, and the method further comprises, in response to an occurrence ofa request for specific data transmission when the radio terminal hasalready been configured by the network to use the second communicationarchitecture type, transmitting data using the first communicationarchitecture type.
 19. (canceled)
 20. (canceled)